Page 1
SECTION-A
1.
? ?
n 1 2 n
r r 1
C k 8 C
?
?
?? if and only if :
(1) 2 2 k 3 ?? (2) 2 3 k 3 2 ??
(3) 2 3 k 3 3 ?? (4) 2 2 k 2 3 ??
Ans. (1)
Sol.
n-1
C
r
= (k
2
– 8)
n
C
r+1
r0
r 1 0, r 0
?
? ? ?
n1
2 r
n
r1
C
k8
C
?
?
??
2
r1
k8
n
?
??
?
2
k 8 0 ??
? ? ? ?
k 2 2 k 2 2 0 ? ? ?
? ? ? ?
k , 2 2 2 2, ? ? ? ? ? ? …(I)
? ? n r 1 ?? ,
r1
1
n
?
?
? k
2
– 8 ??1
k
2
– 9 ??0
–3 ??k ? 3 ….(II)
From equation (I) and (II) we get ?
?
? ?
k 3, 2 2 2 2, 3
??
? ? ? ?
??
2. The distance, of the point (7, –2, 11) from the line
x 6 y 4 z 8
1 0 3
? ? ?
?? along the line
x 5 y 1 z 5
2 3 6
? ? ?
??
?
, is :
(1) 12 (2) 14
(3) 18 (4) 21
Ans. (2)
Sol. B = (2 ? +7, ?3 ? – 2, 6 ? + 11)
Point B lies on
x 6 y 4 z 8
1 0 3
? ? ?
??
2 7 6 3 2 4 6 11 8
1 0 3
? ? ? ? ? ? ? ? ? ?
??
?3 ? – 6 = 0
? = –2
B ? (3, 4, –1)
? ? ? ? ? ?
2 2 2
AB 7 3 4 2 11 1 ? ? ? ? ? ?
16 36 144 ? ? ?
196 14 ??
3. Let x = x(t) and y = y(t) be solutions of the
differential equations
dx
ax 0
dt
?? and
dy
by 0
dt
?? respectively, a, b ? R. Given that
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
for which x(t) = y(t), is :
(1)
2
3
log 2 (2)
4
log 3
(3)
3
log 4
(4)
4
3
log 2
Ans. (4)
Page 2
SECTION-A
1.
? ?
n 1 2 n
r r 1
C k 8 C
?
?
?? if and only if :
(1) 2 2 k 3 ?? (2) 2 3 k 3 2 ??
(3) 2 3 k 3 3 ?? (4) 2 2 k 2 3 ??
Ans. (1)
Sol.
n-1
C
r
= (k
2
– 8)
n
C
r+1
r0
r 1 0, r 0
?
? ? ?
n1
2 r
n
r1
C
k8
C
?
?
??
2
r1
k8
n
?
??
?
2
k 8 0 ??
? ? ? ?
k 2 2 k 2 2 0 ? ? ?
? ? ? ?
k , 2 2 2 2, ? ? ? ? ? ? …(I)
? ? n r 1 ?? ,
r1
1
n
?
?
? k
2
– 8 ??1
k
2
– 9 ??0
–3 ??k ? 3 ….(II)
From equation (I) and (II) we get ?
?
? ?
k 3, 2 2 2 2, 3
??
? ? ? ?
??
2. The distance, of the point (7, –2, 11) from the line
x 6 y 4 z 8
1 0 3
? ? ?
?? along the line
x 5 y 1 z 5
2 3 6
? ? ?
??
?
, is :
(1) 12 (2) 14
(3) 18 (4) 21
Ans. (2)
Sol. B = (2 ? +7, ?3 ? – 2, 6 ? + 11)
Point B lies on
x 6 y 4 z 8
1 0 3
? ? ?
??
2 7 6 3 2 4 6 11 8
1 0 3
? ? ? ? ? ? ? ? ? ?
??
?3 ? – 6 = 0
? = –2
B ? (3, 4, –1)
? ? ? ? ? ?
2 2 2
AB 7 3 4 2 11 1 ? ? ? ? ? ?
16 36 144 ? ? ?
196 14 ??
3. Let x = x(t) and y = y(t) be solutions of the
differential equations
dx
ax 0
dt
?? and
dy
by 0
dt
?? respectively, a, b ? R. Given that
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
for which x(t) = y(t), is :
(1)
2
3
log 2 (2)
4
log 3
(3)
3
log 4
(4)
4
3
log 2
Ans. (4)
Sol.
dx
ax 0
dt
??
dx
adt
x
??
dx
a dt
x
??
??
ln | x | at c ? ? ?
at t = 0, x = 2
ln 2 0 c ??
ln x at ln 2 ? ? ?
at
x
e
2
?
?
at
x 2e
?
? ….(i)
dy
by 0
dt
??
dy
bdt
y
??
ln | y | bt ? ? ? ?
t = 0, y = 1
0 = 0 + ?
y = e
–bt
….(ii)
According to question
3y(1) = 2x(1)
3e
–b
= 2(2 e
–a
)
ab
4
e
3
?
?
For x(t) = y(t)
? 2e
–at
= e
–bt
2 = e
(a – b)t
t
4
2
3
??
?
??
??
4
3
log 2 t ?
4. If (a, b) be the orthocentre of the triangle whose
vertices are (1, 2), (2, 3) and (3, 1), and
? ?
b
2
1
a
I x sin 4x x dx ??
?
,
? ?
b
2
2
a
I sin 4x x dx ??
?
, then
1
2
I
36
I
is equal to :
(1) 72 (2) 88
(3) 80 (4) 66
Ans. (1)
Sol. Equation of CE
y – 1 = ?(x – 3)
x + y = 4
orthocentre lies on the line x + y = 4
so, a + b = 4
? ?
b
1
a
I x sin x(4 x) dx ??
?
…(i)
Using king rule
? ? ? ?
b
1
a
I 4 x sin x(4 x) dx ? ? ?
?
…(ii)
(i) + (ii)
? ?
b
1
a
2I 4sin x(4 x) dx ??
?
2I
1
= 4I
2
I
1
= 2I
2
1
2
I
2
I
?
1
2
36I
72
I
?
5. If A denotes the sum of all the coefficients in the
expansion of (1 – 3x + 10x
2
)
n
and B denotes the
sum of all the coefficients in the expansion of
(1 + x
2
)
n
, then :
(1) A = B
3
(2) 3A = B
(3) B = A
3
(4) A = 3B
Ans. (1)
Sol. Sum of coefficients in the expansion of
(1 – 3x + 10x
2
)
n
= A
then A = (1 – 3 + 10)
n
? 8
n
(put x = 1)
and sum of coefficients in the expansion of
(1 + x
2
)
n
= B
then B = (1 + 1)
n
= 2
n
A = B
3
Page 3
SECTION-A
1.
? ?
n 1 2 n
r r 1
C k 8 C
?
?
?? if and only if :
(1) 2 2 k 3 ?? (2) 2 3 k 3 2 ??
(3) 2 3 k 3 3 ?? (4) 2 2 k 2 3 ??
Ans. (1)
Sol.
n-1
C
r
= (k
2
– 8)
n
C
r+1
r0
r 1 0, r 0
?
? ? ?
n1
2 r
n
r1
C
k8
C
?
?
??
2
r1
k8
n
?
??
?
2
k 8 0 ??
? ? ? ?
k 2 2 k 2 2 0 ? ? ?
? ? ? ?
k , 2 2 2 2, ? ? ? ? ? ? …(I)
? ? n r 1 ?? ,
r1
1
n
?
?
? k
2
– 8 ??1
k
2
– 9 ??0
–3 ??k ? 3 ….(II)
From equation (I) and (II) we get ?
?
? ?
k 3, 2 2 2 2, 3
??
? ? ? ?
??
2. The distance, of the point (7, –2, 11) from the line
x 6 y 4 z 8
1 0 3
? ? ?
?? along the line
x 5 y 1 z 5
2 3 6
? ? ?
??
?
, is :
(1) 12 (2) 14
(3) 18 (4) 21
Ans. (2)
Sol. B = (2 ? +7, ?3 ? – 2, 6 ? + 11)
Point B lies on
x 6 y 4 z 8
1 0 3
? ? ?
??
2 7 6 3 2 4 6 11 8
1 0 3
? ? ? ? ? ? ? ? ? ?
??
?3 ? – 6 = 0
? = –2
B ? (3, 4, –1)
? ? ? ? ? ?
2 2 2
AB 7 3 4 2 11 1 ? ? ? ? ? ?
16 36 144 ? ? ?
196 14 ??
3. Let x = x(t) and y = y(t) be solutions of the
differential equations
dx
ax 0
dt
?? and
dy
by 0
dt
?? respectively, a, b ? R. Given that
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
for which x(t) = y(t), is :
(1)
2
3
log 2 (2)
4
log 3
(3)
3
log 4
(4)
4
3
log 2
Ans. (4)
Sol.
dx
ax 0
dt
??
dx
adt
x
??
dx
a dt
x
??
??
ln | x | at c ? ? ?
at t = 0, x = 2
ln 2 0 c ??
ln x at ln 2 ? ? ?
at
x
e
2
?
?
at
x 2e
?
? ….(i)
dy
by 0
dt
??
dy
bdt
y
??
ln | y | bt ? ? ? ?
t = 0, y = 1
0 = 0 + ?
y = e
–bt
….(ii)
According to question
3y(1) = 2x(1)
3e
–b
= 2(2 e
–a
)
ab
4
e
3
?
?
For x(t) = y(t)
? 2e
–at
= e
–bt
2 = e
(a – b)t
t
4
2
3
??
?
??
??
4
3
log 2 t ?
4. If (a, b) be the orthocentre of the triangle whose
vertices are (1, 2), (2, 3) and (3, 1), and
? ?
b
2
1
a
I x sin 4x x dx ??
?
,
? ?
b
2
2
a
I sin 4x x dx ??
?
, then
1
2
I
36
I
is equal to :
(1) 72 (2) 88
(3) 80 (4) 66
Ans. (1)
Sol. Equation of CE
y – 1 = ?(x – 3)
x + y = 4
orthocentre lies on the line x + y = 4
so, a + b = 4
? ?
b
1
a
I x sin x(4 x) dx ??
?
…(i)
Using king rule
? ? ? ?
b
1
a
I 4 x sin x(4 x) dx ? ? ?
?
…(ii)
(i) + (ii)
? ?
b
1
a
2I 4sin x(4 x) dx ??
?
2I
1
= 4I
2
I
1
= 2I
2
1
2
I
2
I
?
1
2
36I
72
I
?
5. If A denotes the sum of all the coefficients in the
expansion of (1 – 3x + 10x
2
)
n
and B denotes the
sum of all the coefficients in the expansion of
(1 + x
2
)
n
, then :
(1) A = B
3
(2) 3A = B
(3) B = A
3
(4) A = 3B
Ans. (1)
Sol. Sum of coefficients in the expansion of
(1 – 3x + 10x
2
)
n
= A
then A = (1 – 3 + 10)
n
? 8
n
(put x = 1)
and sum of coefficients in the expansion of
(1 + x
2
)
n
= B
then B = (1 + 1)
n
= 2
n
A = B
3
6. The number of common terms in the progressions
4, 9, 14, 19, ...... , up to 25
th
term and 3, 6, 9, 12,
......., up to 37
th
term is :
(1) 9 (2) 5
(3) 7 (4) 8
Ans. (3)
Sol. 4, 9, 14, 19, …., up to 25
th
term
T
25
= 4 + (25 – 1) 5 = 4 + 120 = 124
3, 6, 9, 12, …, up to 37
th
term
T
37
= 3 + (37 – 1)3 = 3 + 108 = 111
Common difference of I
st
series d
1
= 5
Common difference of II
nd
series d
2
= 3
First common term = 9, and
their common difference = 15 (LCM of d
1
and d
2
)
then common terms are
9, 24, 39, 54, 69, 84, 99
7. If the shortest distance of the parabola y
2
= 4x from
the centre of the circle x
2
+ y
2
– 4x – 16y + 64 = 0
is d, then d
2
is equal to :
(1) 16 (2) 24
(3) 20 (4) 36
Ans. (3)
Sol. Equation of normal to parabola
y = mx – 2m – m
3
this normal passing through center of circle (2, 8)
8 = 2m – 2m – m
3
m = –2
So point P on parabola ? (am
2
, –2am) = (4, 4)
And C = (2, 8)
PC = 4 16 20 ??
d
2
= 20
8. If the shortest distance between the lines
x 4 y 1 z
1 2 3
??
??
?
and
x y 1 z 2
2 4 5
? ? ? ?
??
?
is
6
5
, then the sum of all possible values of ? is :
(1) 5 (2) 8
(3) 7 (4) 10
Ans. (2)
Sol.
x 4 y 1 z
1 2 3
??
??
?
x y 1 z 2
2 4 5
? ? ? ?
??
?
the shortest distance between the lines
? ? ? ?
12
12
a b d d
dd
? ? ?
?
?
4 0 2
1 2 3
2 4 5
ˆ
i j k
1 2 3
2 4 5
??
?
?
?
?
?
? ? ? ? ? ? 4 10 12 0 2 4 4
ˆ
2i 1j 0k
? ? ? ? ? ? ?
?
??
? ? 24
6
55
??
?
3 = | ? – 4|
? – 4 = ±3
? = 7, 1
Sum of all possible values of ? is = 8
9. If
1
0
1
dx a b 2 c 3
3 x 1 x
? ? ?
? ? ?
?
, where
a, b, c are rational numbers, then 2a + 3b – 4c is
equal to :
(1) 4 (2) 10
(3) 7 (4) 8
Ans. (4)
Sol.
1
0
1
dx
3 x 1 x ? ? ?
?
? ? ? ?
1
0
3 x 1 x
dx
3 x 1 x
? ? ?
?
? ? ?
?
? ?
11
00
1
3 x dx 1 x dx
2
??
? ? ?
??
??
??
Page 4
SECTION-A
1.
? ?
n 1 2 n
r r 1
C k 8 C
?
?
?? if and only if :
(1) 2 2 k 3 ?? (2) 2 3 k 3 2 ??
(3) 2 3 k 3 3 ?? (4) 2 2 k 2 3 ??
Ans. (1)
Sol.
n-1
C
r
= (k
2
– 8)
n
C
r+1
r0
r 1 0, r 0
?
? ? ?
n1
2 r
n
r1
C
k8
C
?
?
??
2
r1
k8
n
?
??
?
2
k 8 0 ??
? ? ? ?
k 2 2 k 2 2 0 ? ? ?
? ? ? ?
k , 2 2 2 2, ? ? ? ? ? ? …(I)
? ? n r 1 ?? ,
r1
1
n
?
?
? k
2
– 8 ??1
k
2
– 9 ??0
–3 ??k ? 3 ….(II)
From equation (I) and (II) we get ?
?
? ?
k 3, 2 2 2 2, 3
??
? ? ? ?
??
2. The distance, of the point (7, –2, 11) from the line
x 6 y 4 z 8
1 0 3
? ? ?
?? along the line
x 5 y 1 z 5
2 3 6
? ? ?
??
?
, is :
(1) 12 (2) 14
(3) 18 (4) 21
Ans. (2)
Sol. B = (2 ? +7, ?3 ? – 2, 6 ? + 11)
Point B lies on
x 6 y 4 z 8
1 0 3
? ? ?
??
2 7 6 3 2 4 6 11 8
1 0 3
? ? ? ? ? ? ? ? ? ?
??
?3 ? – 6 = 0
? = –2
B ? (3, 4, –1)
? ? ? ? ? ?
2 2 2
AB 7 3 4 2 11 1 ? ? ? ? ? ?
16 36 144 ? ? ?
196 14 ??
3. Let x = x(t) and y = y(t) be solutions of the
differential equations
dx
ax 0
dt
?? and
dy
by 0
dt
?? respectively, a, b ? R. Given that
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
for which x(t) = y(t), is :
(1)
2
3
log 2 (2)
4
log 3
(3)
3
log 4
(4)
4
3
log 2
Ans. (4)
Sol.
dx
ax 0
dt
??
dx
adt
x
??
dx
a dt
x
??
??
ln | x | at c ? ? ?
at t = 0, x = 2
ln 2 0 c ??
ln x at ln 2 ? ? ?
at
x
e
2
?
?
at
x 2e
?
? ….(i)
dy
by 0
dt
??
dy
bdt
y
??
ln | y | bt ? ? ? ?
t = 0, y = 1
0 = 0 + ?
y = e
–bt
….(ii)
According to question
3y(1) = 2x(1)
3e
–b
= 2(2 e
–a
)
ab
4
e
3
?
?
For x(t) = y(t)
? 2e
–at
= e
–bt
2 = e
(a – b)t
t
4
2
3
??
?
??
??
4
3
log 2 t ?
4. If (a, b) be the orthocentre of the triangle whose
vertices are (1, 2), (2, 3) and (3, 1), and
? ?
b
2
1
a
I x sin 4x x dx ??
?
,
? ?
b
2
2
a
I sin 4x x dx ??
?
, then
1
2
I
36
I
is equal to :
(1) 72 (2) 88
(3) 80 (4) 66
Ans. (1)
Sol. Equation of CE
y – 1 = ?(x – 3)
x + y = 4
orthocentre lies on the line x + y = 4
so, a + b = 4
? ?
b
1
a
I x sin x(4 x) dx ??
?
…(i)
Using king rule
? ? ? ?
b
1
a
I 4 x sin x(4 x) dx ? ? ?
?
…(ii)
(i) + (ii)
? ?
b
1
a
2I 4sin x(4 x) dx ??
?
2I
1
= 4I
2
I
1
= 2I
2
1
2
I
2
I
?
1
2
36I
72
I
?
5. If A denotes the sum of all the coefficients in the
expansion of (1 – 3x + 10x
2
)
n
and B denotes the
sum of all the coefficients in the expansion of
(1 + x
2
)
n
, then :
(1) A = B
3
(2) 3A = B
(3) B = A
3
(4) A = 3B
Ans. (1)
Sol. Sum of coefficients in the expansion of
(1 – 3x + 10x
2
)
n
= A
then A = (1 – 3 + 10)
n
? 8
n
(put x = 1)
and sum of coefficients in the expansion of
(1 + x
2
)
n
= B
then B = (1 + 1)
n
= 2
n
A = B
3
6. The number of common terms in the progressions
4, 9, 14, 19, ...... , up to 25
th
term and 3, 6, 9, 12,
......., up to 37
th
term is :
(1) 9 (2) 5
(3) 7 (4) 8
Ans. (3)
Sol. 4, 9, 14, 19, …., up to 25
th
term
T
25
= 4 + (25 – 1) 5 = 4 + 120 = 124
3, 6, 9, 12, …, up to 37
th
term
T
37
= 3 + (37 – 1)3 = 3 + 108 = 111
Common difference of I
st
series d
1
= 5
Common difference of II
nd
series d
2
= 3
First common term = 9, and
their common difference = 15 (LCM of d
1
and d
2
)
then common terms are
9, 24, 39, 54, 69, 84, 99
7. If the shortest distance of the parabola y
2
= 4x from
the centre of the circle x
2
+ y
2
– 4x – 16y + 64 = 0
is d, then d
2
is equal to :
(1) 16 (2) 24
(3) 20 (4) 36
Ans. (3)
Sol. Equation of normal to parabola
y = mx – 2m – m
3
this normal passing through center of circle (2, 8)
8 = 2m – 2m – m
3
m = –2
So point P on parabola ? (am
2
, –2am) = (4, 4)
And C = (2, 8)
PC = 4 16 20 ??
d
2
= 20
8. If the shortest distance between the lines
x 4 y 1 z
1 2 3
??
??
?
and
x y 1 z 2
2 4 5
? ? ? ?
??
?
is
6
5
, then the sum of all possible values of ? is :
(1) 5 (2) 8
(3) 7 (4) 10
Ans. (2)
Sol.
x 4 y 1 z
1 2 3
??
??
?
x y 1 z 2
2 4 5
? ? ? ?
??
?
the shortest distance between the lines
? ? ? ?
12
12
a b d d
dd
? ? ?
?
?
4 0 2
1 2 3
2 4 5
ˆ
i j k
1 2 3
2 4 5
??
?
?
?
?
?
? ? ? ? ? ? 4 10 12 0 2 4 4
ˆ
2i 1j 0k
? ? ? ? ? ? ?
?
??
? ? 24
6
55
??
?
3 = | ? – 4|
? – 4 = ±3
? = 7, 1
Sum of all possible values of ? is = 8
9. If
1
0
1
dx a b 2 c 3
3 x 1 x
? ? ?
? ? ?
?
, where
a, b, c are rational numbers, then 2a + 3b – 4c is
equal to :
(1) 4 (2) 10
(3) 7 (4) 8
Ans. (4)
Sol.
1
0
1
dx
3 x 1 x ? ? ?
?
? ? ? ?
1
0
3 x 1 x
dx
3 x 1 x
? ? ?
?
? ? ?
?
? ?
11
00
1
3 x dx 1 x dx
2
??
? ? ?
??
??
??
? ? ? ?
1
33
22
0
3 x 2 1 x
1
2
2 3 3
??
??
??
?
??
??
??
? ?
3
2
1 2 2
8 3 3 2 1
2 3 3
?? ??
? ? ?
?? ??
??
?? ??
1
8 3 3 2 2 1
3
??
? ? ?
??
2
3 3 2 a b 2 c 3
3
? ? ? ? ? ?
2
a 3, b , c 1
3
? ? ? ? ?
2a + 3b – 4c = 6 – 2 + 4 = 8
10. Let S = {l, 2, 3, ... , 10}. Suppose M is the set of all
the subsets of S, then the relation
R = {(A, B): A ? B ? ?; A, B ? M} is :
(1) symmetric and reflexive only
(2) reflexive only
(3) symmetric and transitive only
(4) symmetric only
Ans. (4)
Sol. Let S = {1, 2, 3, …, 10}
R = {(A, B): A ? B ? ?; A, B ? M}
For Reflexive,
M is subset of ‘S’
So ? ?? M
for ? ? ? = ?
? but relation is A ? B ? ?
So it is not reflexive.
For symmetric,
ARB A ? B ? ?,
? BRA ? B ? A ? ?,
So it is symmetric.
For transitive,
If A = {(1, 2), (2, 3)}
B = {(2, 3), (3, 4)}
C = {(3, 4), (5, 6)}
ARB & BRC but A does not relate to C
So it not transitive
11. If S = {z ? C : |z – i| = |z + i| = |z–1|}, then, n(S) is:
(1) 1 (2) 0
(3) 3 (4) 2
Ans. (1)
Sol. |z – i| = |z + i| = |z – 1|
ABC is a triangle. Hence its circum-centre will be
the only point whose distance from A, B, C will be
same.
So n(S) = 1
12. Four distinct points (2k, 3k), (1, 0), (0, 1) and
(0, 0) lie on a circle for k equal to :
(1)
2
13
(2)
3
13
(3)
5
13
(4)
1
13
Ans. (3)
Sol. (2k, 3k) will lie on circle whose diameter is AB.
(x – 1) (x) + (y – 1) (y) = 0
x
2
+ y
2
– x – y = 0 …(i)
Satisfy (2k, 3k) in (i)
(2k)
2
+ (3k)
2
– 2k – 3k = 0
13k
2
– 5k = 0
k = 0,
5
k
13
?
hence
5
k
13
?
Page 5
SECTION-A
1.
? ?
n 1 2 n
r r 1
C k 8 C
?
?
?? if and only if :
(1) 2 2 k 3 ?? (2) 2 3 k 3 2 ??
(3) 2 3 k 3 3 ?? (4) 2 2 k 2 3 ??
Ans. (1)
Sol.
n-1
C
r
= (k
2
– 8)
n
C
r+1
r0
r 1 0, r 0
?
? ? ?
n1
2 r
n
r1
C
k8
C
?
?
??
2
r1
k8
n
?
??
?
2
k 8 0 ??
? ? ? ?
k 2 2 k 2 2 0 ? ? ?
? ? ? ?
k , 2 2 2 2, ? ? ? ? ? ? …(I)
? ? n r 1 ?? ,
r1
1
n
?
?
? k
2
– 8 ??1
k
2
– 9 ??0
–3 ??k ? 3 ….(II)
From equation (I) and (II) we get ?
?
? ?
k 3, 2 2 2 2, 3
??
? ? ? ?
??
2. The distance, of the point (7, –2, 11) from the line
x 6 y 4 z 8
1 0 3
? ? ?
?? along the line
x 5 y 1 z 5
2 3 6
? ? ?
??
?
, is :
(1) 12 (2) 14
(3) 18 (4) 21
Ans. (2)
Sol. B = (2 ? +7, ?3 ? – 2, 6 ? + 11)
Point B lies on
x 6 y 4 z 8
1 0 3
? ? ?
??
2 7 6 3 2 4 6 11 8
1 0 3
? ? ? ? ? ? ? ? ? ?
??
?3 ? – 6 = 0
? = –2
B ? (3, 4, –1)
? ? ? ? ? ?
2 2 2
AB 7 3 4 2 11 1 ? ? ? ? ? ?
16 36 144 ? ? ?
196 14 ??
3. Let x = x(t) and y = y(t) be solutions of the
differential equations
dx
ax 0
dt
?? and
dy
by 0
dt
?? respectively, a, b ? R. Given that
x(0) = 2; y(0) = 1 and 3y(1) = 2x(1), the value of t,
for which x(t) = y(t), is :
(1)
2
3
log 2 (2)
4
log 3
(3)
3
log 4
(4)
4
3
log 2
Ans. (4)
Sol.
dx
ax 0
dt
??
dx
adt
x
??
dx
a dt
x
??
??
ln | x | at c ? ? ?
at t = 0, x = 2
ln 2 0 c ??
ln x at ln 2 ? ? ?
at
x
e
2
?
?
at
x 2e
?
? ….(i)
dy
by 0
dt
??
dy
bdt
y
??
ln | y | bt ? ? ? ?
t = 0, y = 1
0 = 0 + ?
y = e
–bt
….(ii)
According to question
3y(1) = 2x(1)
3e
–b
= 2(2 e
–a
)
ab
4
e
3
?
?
For x(t) = y(t)
? 2e
–at
= e
–bt
2 = e
(a – b)t
t
4
2
3
??
?
??
??
4
3
log 2 t ?
4. If (a, b) be the orthocentre of the triangle whose
vertices are (1, 2), (2, 3) and (3, 1), and
? ?
b
2
1
a
I x sin 4x x dx ??
?
,
? ?
b
2
2
a
I sin 4x x dx ??
?
, then
1
2
I
36
I
is equal to :
(1) 72 (2) 88
(3) 80 (4) 66
Ans. (1)
Sol. Equation of CE
y – 1 = ?(x – 3)
x + y = 4
orthocentre lies on the line x + y = 4
so, a + b = 4
? ?
b
1
a
I x sin x(4 x) dx ??
?
…(i)
Using king rule
? ? ? ?
b
1
a
I 4 x sin x(4 x) dx ? ? ?
?
…(ii)
(i) + (ii)
? ?
b
1
a
2I 4sin x(4 x) dx ??
?
2I
1
= 4I
2
I
1
= 2I
2
1
2
I
2
I
?
1
2
36I
72
I
?
5. If A denotes the sum of all the coefficients in the
expansion of (1 – 3x + 10x
2
)
n
and B denotes the
sum of all the coefficients in the expansion of
(1 + x
2
)
n
, then :
(1) A = B
3
(2) 3A = B
(3) B = A
3
(4) A = 3B
Ans. (1)
Sol. Sum of coefficients in the expansion of
(1 – 3x + 10x
2
)
n
= A
then A = (1 – 3 + 10)
n
? 8
n
(put x = 1)
and sum of coefficients in the expansion of
(1 + x
2
)
n
= B
then B = (1 + 1)
n
= 2
n
A = B
3
6. The number of common terms in the progressions
4, 9, 14, 19, ...... , up to 25
th
term and 3, 6, 9, 12,
......., up to 37
th
term is :
(1) 9 (2) 5
(3) 7 (4) 8
Ans. (3)
Sol. 4, 9, 14, 19, …., up to 25
th
term
T
25
= 4 + (25 – 1) 5 = 4 + 120 = 124
3, 6, 9, 12, …, up to 37
th
term
T
37
= 3 + (37 – 1)3 = 3 + 108 = 111
Common difference of I
st
series d
1
= 5
Common difference of II
nd
series d
2
= 3
First common term = 9, and
their common difference = 15 (LCM of d
1
and d
2
)
then common terms are
9, 24, 39, 54, 69, 84, 99
7. If the shortest distance of the parabola y
2
= 4x from
the centre of the circle x
2
+ y
2
– 4x – 16y + 64 = 0
is d, then d
2
is equal to :
(1) 16 (2) 24
(3) 20 (4) 36
Ans. (3)
Sol. Equation of normal to parabola
y = mx – 2m – m
3
this normal passing through center of circle (2, 8)
8 = 2m – 2m – m
3
m = –2
So point P on parabola ? (am
2
, –2am) = (4, 4)
And C = (2, 8)
PC = 4 16 20 ??
d
2
= 20
8. If the shortest distance between the lines
x 4 y 1 z
1 2 3
??
??
?
and
x y 1 z 2
2 4 5
? ? ? ?
??
?
is
6
5
, then the sum of all possible values of ? is :
(1) 5 (2) 8
(3) 7 (4) 10
Ans. (2)
Sol.
x 4 y 1 z
1 2 3
??
??
?
x y 1 z 2
2 4 5
? ? ? ?
??
?
the shortest distance between the lines
? ? ? ?
12
12
a b d d
dd
? ? ?
?
?
4 0 2
1 2 3
2 4 5
ˆ
i j k
1 2 3
2 4 5
??
?
?
?
?
?
? ? ? ? ? ? 4 10 12 0 2 4 4
ˆ
2i 1j 0k
? ? ? ? ? ? ?
?
??
? ? 24
6
55
??
?
3 = | ? – 4|
? – 4 = ±3
? = 7, 1
Sum of all possible values of ? is = 8
9. If
1
0
1
dx a b 2 c 3
3 x 1 x
? ? ?
? ? ?
?
, where
a, b, c are rational numbers, then 2a + 3b – 4c is
equal to :
(1) 4 (2) 10
(3) 7 (4) 8
Ans. (4)
Sol.
1
0
1
dx
3 x 1 x ? ? ?
?
? ? ? ?
1
0
3 x 1 x
dx
3 x 1 x
? ? ?
?
? ? ?
?
? ?
11
00
1
3 x dx 1 x dx
2
??
? ? ?
??
??
??
? ? ? ?
1
33
22
0
3 x 2 1 x
1
2
2 3 3
??
??
??
?
??
??
??
? ?
3
2
1 2 2
8 3 3 2 1
2 3 3
?? ??
? ? ?
?? ??
??
?? ??
1
8 3 3 2 2 1
3
??
? ? ?
??
2
3 3 2 a b 2 c 3
3
? ? ? ? ? ?
2
a 3, b , c 1
3
? ? ? ? ?
2a + 3b – 4c = 6 – 2 + 4 = 8
10. Let S = {l, 2, 3, ... , 10}. Suppose M is the set of all
the subsets of S, then the relation
R = {(A, B): A ? B ? ?; A, B ? M} is :
(1) symmetric and reflexive only
(2) reflexive only
(3) symmetric and transitive only
(4) symmetric only
Ans. (4)
Sol. Let S = {1, 2, 3, …, 10}
R = {(A, B): A ? B ? ?; A, B ? M}
For Reflexive,
M is subset of ‘S’
So ? ?? M
for ? ? ? = ?
? but relation is A ? B ? ?
So it is not reflexive.
For symmetric,
ARB A ? B ? ?,
? BRA ? B ? A ? ?,
So it is symmetric.
For transitive,
If A = {(1, 2), (2, 3)}
B = {(2, 3), (3, 4)}
C = {(3, 4), (5, 6)}
ARB & BRC but A does not relate to C
So it not transitive
11. If S = {z ? C : |z – i| = |z + i| = |z–1|}, then, n(S) is:
(1) 1 (2) 0
(3) 3 (4) 2
Ans. (1)
Sol. |z – i| = |z + i| = |z – 1|
ABC is a triangle. Hence its circum-centre will be
the only point whose distance from A, B, C will be
same.
So n(S) = 1
12. Four distinct points (2k, 3k), (1, 0), (0, 1) and
(0, 0) lie on a circle for k equal to :
(1)
2
13
(2)
3
13
(3)
5
13
(4)
1
13
Ans. (3)
Sol. (2k, 3k) will lie on circle whose diameter is AB.
(x – 1) (x) + (y – 1) (y) = 0
x
2
+ y
2
– x – y = 0 …(i)
Satisfy (2k, 3k) in (i)
(2k)
2
+ (3k)
2
– 2k – 3k = 0
13k
2
– 5k = 0
k = 0,
5
k
13
?
hence
5
k
13
?
13. Consider the function.
? ?
? ?
2
2
sin x 3
x [x]
a 7x 12 x
, x 3
b x 7x 12
f (x) 2 , x 3
b , x 3
?
?
?
??
? ?
??
?
?
?
??
?
?
?
?
?
?
?
Where [x] denotes the greatest integer less than or
equal to x. If S denotes the set of all ordered pairs
(a, b) such that f(x) is continuous at x = 3, then the
number of elements in S is :
(1) 2 (2) Infinitely many
(3) 4 (4) 1
Ans. (4)
Sol.
? ?
? ?
2
2
7x 12 x
a
f3
b x 7x 12
?
??
?
??
(for f(x) to be cont.)
? f(3
–
) =
? ? ? ?
? ? ? ?
x 3 x 4
a
;x 3
b x 3 x 4
??
?
?
??
?
a
b
?
Hence
? ?
a
f3
b
?
?
?
Then
? ?
? ?
x3
sin x 3
lim
x3
f 3 2 2
?
?
? ??
??
??
? ?
??
?? and
f(3) = b.
Hence f(3) = f(3
+
) = f(3
–
)
? b = 2 =
a
b
?
b = 2, a = –4
Hence only 1 ordered pair (–4, 2).
14. Let a
1
, a
2
, ….. a
10
be 10 observations such that
10
k
k1
a 50
?
?
?
and
kj
kj
a a 1100
??
??
?
. Then the
standard deviation of a
1
, a
2
, .., a
10
is equal to :
(1) 5 (2) 5
(3) 10 (4) 115
Ans. (2)
Sol.
10
k
k1
a 50
?
?
?
a
1
+ a
2
+ … + a
10
= 50 ….(i)
kj
kj
a a 1100
??
?
?
....(ii)
If a
1
+ a
2
+ … + a
10
= 50.
(a
1
+ a
2
+ … + a
10
)
2
= 2500
?
10
2
i k j
i 1 k j
a 2 a a 2500
??
??
??
? ? ?
10
2
i
i1
a 2500 2 1100
?
??
?
10
2
i
i1
a 300
?
?
?
, Standard deviation ‘ ?’
2
2
2
ii
aa
300 50
10 10 10 10
??
??
??
?? ? ? ? ?
??
?? ??
??
??
??
30 25 5 ? ? ?
15. The length of the chord of the ellipse
22
xy
1
25 16
?? ,
whose mid point is
2
1,
5
??
??
??
, is equal to :
(1)
1691
5
(2)
2009
5
(3)
1741
5
(4)
1541
5
Ans. (1)
Sol. Equation of chord with given middle point.
T = S
1
x y 1 1
25 40 25 100
? ? ?
8x 5y 8 2
200 200
??
?
10 8x
y
5
?
? …(i)
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