Page 1
Answers & Solutions
for
JEE (Main)-2023 (Online) Phase-2
(Mathematics, Physics and Chemistry)
13/04/2023
Morning
Time : 3 hrs. M.M. : 300
IMPORTANT INSTRUCTIONS:
(1) The test is of 3 hours duration.
(2) The Test Booklet consists of 90 questions. The maximum marks are 300.
(3) There are three parts in the question paper consisting of Mathematics, Physics and Chemistry
having 30 questions in each part of equal weightage. Each part (subject) has two sections.
(i) Section-A: This section contains 20 multiple choice questions which have only one correct
answer. Each question carries 4 marks for correct answer and –1 mark for wrong answer.
(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out
of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks
for correct answer and –1 mark for wrong answer. For Section-B, the answer should be
rounded off to the nearest integer.
Page 2
Answers & Solutions
for
JEE (Main)-2023 (Online) Phase-2
(Mathematics, Physics and Chemistry)
13/04/2023
Morning
Time : 3 hrs. M.M. : 300
IMPORTANT INSTRUCTIONS:
(1) The test is of 3 hours duration.
(2) The Test Booklet consists of 90 questions. The maximum marks are 300.
(3) There are three parts in the question paper consisting of Mathematics, Physics and Chemistry
having 30 questions in each part of equal weightage. Each part (subject) has two sections.
(i) Section-A: This section contains 20 multiple choice questions which have only one correct
answer. Each question carries 4 marks for correct answer and –1 mark for wrong answer.
(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out
of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks
for correct answer and –1 mark for wrong answer. For Section-B, the answer should be
rounded off to the nearest integer.
MATHEMATICS
SECTION - A
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4 choices
(1), (2), (3) and (4), out of which ONLY ONE is correct.
Choose the correct answer:
1. The number of symmetric matrices of order 3, with
all the entries from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
is
(1) 6
10
(2) 10
6
(3) 9
10
(4) 10
9
Answer (2)
Sol. A = {0, 1, 2, 3, …8, 9}
* * *
0 **
00 *
M
??
??
=
??
??
??
? Total symmetric matrix = 10
6
2. Let
13
1 2 3 , 2
4
B
? ??
??
= ? ?
??
?? ??
??
be the adjoint of a matrix A
and |A| = 2. Then ? ? 2 2 B
? ??
??
? - ? ? - ?
??
?? ?
??
is equal to
(1) 0 (2) 16
(3) –16 (4) 32
Answer (3)
Sol.
3 1
3 1 2 , 2
4
B
??
?
??
= ? ?
??
??
??
??
And adj (A) = B, |A| = 2
? |adj (A)| = |B|
? 2
2
= (8 – 3?) – 3(4 – 3?) + ?(–?)
? ?
2
– 6? + 8 = 0
? (? – 4) (? – 2) = 0
? = 4, 2 but ? > 2 so 4 ?=
Now
? ? ? ?
3 14 4
3 2 2 4 8 4 1 2 8
444 4
B
?? ? ? ? ?
?
?? ? ? ? ?
? - ? ? - ? = - -
?? ? ? ? ?
?? ? ? ? ?
?
? ? ? ? ??
? ?
4
12 12 8 8
4
??
??
=-
??
??
??
? ? 48 96 32 16 - + = -
3. Among
( ) ( )
2
1
1 : lim 2 4 6 ... 2 1
n
Sn
n
??
+ + + + =
( )
( )
15 15 15 15
16
11
2 : lim 1 2 3 ...
16 n
Sn
n
??
+ + + + =
(1) Both (S1) and (S2) are true
(2) Only (S1) is true
(3) Both (S1) and (S2) are false
(4) Only (S2) is true
Answer (1)
Sol.
? ?
1
2
1
: lim 2 4 6 ... 2
n
Sn
n
??
+ + + +
( )
2
1
lim 2 1
2
n
nn
n
??
+
=
( )
15 15 15 15
2
16
1
: lim 1 2 3 ...
n
Sn
n
??
+ + + +
?
1
1
1
lim
1
n
k
r
k
n
r
k
n
=
+
??
=
+
?
Hence k = 15
?
15
1
16
1
lim
16
n
r
n
r
n
=
??
=
?
? Both S1 and S2 are correct
Page 3
Answers & Solutions
for
JEE (Main)-2023 (Online) Phase-2
(Mathematics, Physics and Chemistry)
13/04/2023
Morning
Time : 3 hrs. M.M. : 300
IMPORTANT INSTRUCTIONS:
(1) The test is of 3 hours duration.
(2) The Test Booklet consists of 90 questions. The maximum marks are 300.
(3) There are three parts in the question paper consisting of Mathematics, Physics and Chemistry
having 30 questions in each part of equal weightage. Each part (subject) has two sections.
(i) Section-A: This section contains 20 multiple choice questions which have only one correct
answer. Each question carries 4 marks for correct answer and –1 mark for wrong answer.
(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out
of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks
for correct answer and –1 mark for wrong answer. For Section-B, the answer should be
rounded off to the nearest integer.
MATHEMATICS
SECTION - A
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4 choices
(1), (2), (3) and (4), out of which ONLY ONE is correct.
Choose the correct answer:
1. The number of symmetric matrices of order 3, with
all the entries from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
is
(1) 6
10
(2) 10
6
(3) 9
10
(4) 10
9
Answer (2)
Sol. A = {0, 1, 2, 3, …8, 9}
* * *
0 **
00 *
M
??
??
=
??
??
??
? Total symmetric matrix = 10
6
2. Let
13
1 2 3 , 2
4
B
? ??
??
= ? ?
??
?? ??
??
be the adjoint of a matrix A
and |A| = 2. Then ? ? 2 2 B
? ??
??
? - ? ? - ?
??
?? ?
??
is equal to
(1) 0 (2) 16
(3) –16 (4) 32
Answer (3)
Sol.
3 1
3 1 2 , 2
4
B
??
?
??
= ? ?
??
??
??
??
And adj (A) = B, |A| = 2
? |adj (A)| = |B|
? 2
2
= (8 – 3?) – 3(4 – 3?) + ?(–?)
? ?
2
– 6? + 8 = 0
? (? – 4) (? – 2) = 0
? = 4, 2 but ? > 2 so 4 ?=
Now
? ? ? ?
3 14 4
3 2 2 4 8 4 1 2 8
444 4
B
?? ? ? ? ?
?
?? ? ? ? ?
? - ? ? - ? = - -
?? ? ? ? ?
?? ? ? ? ?
?
? ? ? ? ??
? ?
4
12 12 8 8
4
??
??
=-
??
??
??
? ? 48 96 32 16 - + = -
3. Among
( ) ( )
2
1
1 : lim 2 4 6 ... 2 1
n
Sn
n
??
+ + + + =
( )
( )
15 15 15 15
16
11
2 : lim 1 2 3 ...
16 n
Sn
n
??
+ + + + =
(1) Both (S1) and (S2) are true
(2) Only (S1) is true
(3) Both (S1) and (S2) are false
(4) Only (S2) is true
Answer (1)
Sol.
? ?
1
2
1
: lim 2 4 6 ... 2
n
Sn
n
??
+ + + +
( )
2
1
lim 2 1
2
n
nn
n
??
+
=
( )
15 15 15 15
2
16
1
: lim 1 2 3 ...
n
Sn
n
??
+ + + +
?
1
1
1
lim
1
n
k
r
k
n
r
k
n
=
+
??
=
+
?
Hence k = 15
?
15
1
16
1
lim
16
n
r
n
r
n
=
??
=
?
? Both S1 and S2 are correct
4. Fractional part of the number
2022
4
15
is equal to
(1)
8
15
(2)
4
15
(3)
14
15
(4)
1
15
Answer (4)
Sol.
2022
4
15
4 4 (mod 15) ?
2
4 1(mod 15) ?
2022
4 1(mod 15) ?
? Fractional part of
2022
41
15 15
=
5.
0
1
max 2sin cos sin3
3 x
x x x x
? ??
??
- + =
??
??
(1)
2 3 3
6
? + -
(2) ?
(3) 0 (4)
5 2 3 3
6
? + +
Answer (4)
Sol. ( ) 1 2cos2 cos3 f x x x ? = - +
( ) 4sin2 3sin3 f x x x ??=-
( ) 0 fx ? =
( )
23
1 2 2cos 1 4cos 3cos 0 x x x ? - - + - =
( )( )
( ) 2cos 3 2cos 3 cos 1 0 x x x + - - =
– 3 3
cos , , 1
22
x =
5
, , 0
66
x
??
=
5
2 3 3 0
6
f
? ??
?? = - - ?
??
??
2 3 3 0
6
f
? ??
?? = - ?
??
??
(0) 0 f ?? =
So
5
6
x
?
= is local maxima point
Maximum value of
5 5 3 1
()
6 6 2 3
f x f
?? ??
= = + +
??
??
5 2 3 3
6
? + +
=
6. The negation of the statement ( ) ( ( ) A B C ??
( )) A B A ? ? ? is
(1) equivalent to ~ C
(2) equivalent to ~ BC ?
(3) a fallacy
(4) equivalent to ~ A
Answer (4)
Sol. ( ) ( ) ( ) A B C A B A ? ? ? ? ?
( ) ( ) ( ) ( )
~~ A B C A B A ? ? ? ? ?
( ) ( ) ( ) ~ A B C A B A ? ? ? ? ?
= A
? Negation of statement = ~A
7. For , x ? two real valued functions () fx and () gx
are such that, ( ) 1 g x x =+ and
( ) 3 fog x x x = + - . Then (0) f is equal to
(1) 1 (2) 5
(3) 0 (4) –3
Answer (2)
Sol. ( ) ( )
3 f g x x x = + -
( )
13 f x x x + = + -
Put 1 xt +=
1 xt =-
x = (t – 1)
2
f(t) = (t – 1)
2
+ 3 – (t – 1)
f(0) = 1 + 3 + 1 = 5
Page 4
Answers & Solutions
for
JEE (Main)-2023 (Online) Phase-2
(Mathematics, Physics and Chemistry)
13/04/2023
Morning
Time : 3 hrs. M.M. : 300
IMPORTANT INSTRUCTIONS:
(1) The test is of 3 hours duration.
(2) The Test Booklet consists of 90 questions. The maximum marks are 300.
(3) There are three parts in the question paper consisting of Mathematics, Physics and Chemistry
having 30 questions in each part of equal weightage. Each part (subject) has two sections.
(i) Section-A: This section contains 20 multiple choice questions which have only one correct
answer. Each question carries 4 marks for correct answer and –1 mark for wrong answer.
(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out
of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks
for correct answer and –1 mark for wrong answer. For Section-B, the answer should be
rounded off to the nearest integer.
MATHEMATICS
SECTION - A
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4 choices
(1), (2), (3) and (4), out of which ONLY ONE is correct.
Choose the correct answer:
1. The number of symmetric matrices of order 3, with
all the entries from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
is
(1) 6
10
(2) 10
6
(3) 9
10
(4) 10
9
Answer (2)
Sol. A = {0, 1, 2, 3, …8, 9}
* * *
0 **
00 *
M
??
??
=
??
??
??
? Total symmetric matrix = 10
6
2. Let
13
1 2 3 , 2
4
B
? ??
??
= ? ?
??
?? ??
??
be the adjoint of a matrix A
and |A| = 2. Then ? ? 2 2 B
? ??
??
? - ? ? - ?
??
?? ?
??
is equal to
(1) 0 (2) 16
(3) –16 (4) 32
Answer (3)
Sol.
3 1
3 1 2 , 2
4
B
??
?
??
= ? ?
??
??
??
??
And adj (A) = B, |A| = 2
? |adj (A)| = |B|
? 2
2
= (8 – 3?) – 3(4 – 3?) + ?(–?)
? ?
2
– 6? + 8 = 0
? (? – 4) (? – 2) = 0
? = 4, 2 but ? > 2 so 4 ?=
Now
? ? ? ?
3 14 4
3 2 2 4 8 4 1 2 8
444 4
B
?? ? ? ? ?
?
?? ? ? ? ?
? - ? ? - ? = - -
?? ? ? ? ?
?? ? ? ? ?
?
? ? ? ? ??
? ?
4
12 12 8 8
4
??
??
=-
??
??
??
? ? 48 96 32 16 - + = -
3. Among
( ) ( )
2
1
1 : lim 2 4 6 ... 2 1
n
Sn
n
??
+ + + + =
( )
( )
15 15 15 15
16
11
2 : lim 1 2 3 ...
16 n
Sn
n
??
+ + + + =
(1) Both (S1) and (S2) are true
(2) Only (S1) is true
(3) Both (S1) and (S2) are false
(4) Only (S2) is true
Answer (1)
Sol.
? ?
1
2
1
: lim 2 4 6 ... 2
n
Sn
n
??
+ + + +
( )
2
1
lim 2 1
2
n
nn
n
??
+
=
( )
15 15 15 15
2
16
1
: lim 1 2 3 ...
n
Sn
n
??
+ + + +
?
1
1
1
lim
1
n
k
r
k
n
r
k
n
=
+
??
=
+
?
Hence k = 15
?
15
1
16
1
lim
16
n
r
n
r
n
=
??
=
?
? Both S1 and S2 are correct
4. Fractional part of the number
2022
4
15
is equal to
(1)
8
15
(2)
4
15
(3)
14
15
(4)
1
15
Answer (4)
Sol.
2022
4
15
4 4 (mod 15) ?
2
4 1(mod 15) ?
2022
4 1(mod 15) ?
? Fractional part of
2022
41
15 15
=
5.
0
1
max 2sin cos sin3
3 x
x x x x
? ??
??
- + =
??
??
(1)
2 3 3
6
? + -
(2) ?
(3) 0 (4)
5 2 3 3
6
? + +
Answer (4)
Sol. ( ) 1 2cos2 cos3 f x x x ? = - +
( ) 4sin2 3sin3 f x x x ??=-
( ) 0 fx ? =
( )
23
1 2 2cos 1 4cos 3cos 0 x x x ? - - + - =
( )( )
( ) 2cos 3 2cos 3 cos 1 0 x x x + - - =
– 3 3
cos , , 1
22
x =
5
, , 0
66
x
??
=
5
2 3 3 0
6
f
? ??
?? = - - ?
??
??
2 3 3 0
6
f
? ??
?? = - ?
??
??
(0) 0 f ?? =
So
5
6
x
?
= is local maxima point
Maximum value of
5 5 3 1
()
6 6 2 3
f x f
?? ??
= = + +
??
??
5 2 3 3
6
? + +
=
6. The negation of the statement ( ) ( ( ) A B C ??
( )) A B A ? ? ? is
(1) equivalent to ~ C
(2) equivalent to ~ BC ?
(3) a fallacy
(4) equivalent to ~ A
Answer (4)
Sol. ( ) ( ) ( ) A B C A B A ? ? ? ? ?
( ) ( ) ( ) ( )
~~ A B C A B A ? ? ? ? ?
( ) ( ) ( ) ~ A B C A B A ? ? ? ? ?
= A
? Negation of statement = ~A
7. For , x ? two real valued functions () fx and () gx
are such that, ( ) 1 g x x =+ and
( ) 3 fog x x x = + - . Then (0) f is equal to
(1) 1 (2) 5
(3) 0 (4) –3
Answer (2)
Sol. ( ) ( )
3 f g x x x = + -
( )
13 f x x x + = + -
Put 1 xt +=
1 xt =-
x = (t – 1)
2
f(t) = (t – 1)
2
+ 3 – (t – 1)
f(0) = 1 + 3 + 1 = 5
8. Let
1 2 3 10
, , ...., s s s s respectively be the sum of 12
terms of 10 A.Ps whose first terms are 1, 2, 3,....,10
and the common differences are 1, 3, 5,...,19
respectively. Then
10
1
i
i
s
=
?
is equal to
(1) 7220
(2) 7360
(3) 7260
(4) 7380
Answer (3)
Sol. 1 10 r ??
( )( ) ( )
12
2 12 1 2 1 6 2 22 11
2
i
S r r r r ?? = + - - = + -
??
= 6(24r – 11)
( ) ? ?
10 10
11
10
6 24 11 6 24 11 240 11
2
r
rr
Sr
==
= - = ? - + -
??
= 30 (242) = 7260
9. Let the equation of plane passing through the line
of intersection of the planes 22 x y az + + = and
3 x y z - + = be 5 11 6 1 x y bz a - + = - . For c ? ,
if the distance of this plane from the point ( , , ) a c c -
is
2
,
a
then
ab
c
+
is equal to
(1) 2 (2) 4
(3) – 4 (4) – 2
Answer (3)
Sol. Let the equation of plane passing through the
intersection of two given planes:
x + 2y + az – 2 + ?(x – y + z – 3) = 0
? x(? + 1) + y(2 – ?) + z(a + ?) –2 –3? = 0
This is same as 5x –11y + bz = 6a – 1
1 2 2 3
5 11 6 1
a
ba
? + - ? + ? + ?
= = =
--
? –11? – 11 = 10 – 5?
?
7
6 21
2
-
? = - ? ? =
7 21
22
2 2 3
22
11 6 1 11 6 1 aa
+-
- ? + ?
= ? =
- - - -
?
( )
1 17
6 1 17 3
2 2 6 1
aa
a
-
- = ? - = ? =
-
7
3
21
2
11 2
a
bb
-
- ? + ?
= ? - =
-
?
1
1
22
b
b - = - ? =
? point (a, – c, c) ? (3, – c, c)
Distance
22
3 a
==
Plane: 5x – 11y + z = 17
15 11 17 2
147 3
cc + + -
=
? |12c – 2| = 14
? c = – 1,
4
3
c = – 1 ( ) c ?
?
31
4
1
ab
c
++
= = -
-
10. Let PQ be a focal chord of the parabola
2
36 yx =
of length 100, making an acute angle with the
positive x-axis. Let the ordinate of P be positive and
M be the point on the line segment PQ such that
PM : MQ = 3 : 1. Then which of the following points
does NOT lie on the line passing through M and
perpendicular to the line PQ?
(1) ( 6, 45) - (2) (6, 29)
(3) (3, 33) (4) ( 3, 43) -
Answer (4)
Sol.
Page 5
Answers & Solutions
for
JEE (Main)-2023 (Online) Phase-2
(Mathematics, Physics and Chemistry)
13/04/2023
Morning
Time : 3 hrs. M.M. : 300
IMPORTANT INSTRUCTIONS:
(1) The test is of 3 hours duration.
(2) The Test Booklet consists of 90 questions. The maximum marks are 300.
(3) There are three parts in the question paper consisting of Mathematics, Physics and Chemistry
having 30 questions in each part of equal weightage. Each part (subject) has two sections.
(i) Section-A: This section contains 20 multiple choice questions which have only one correct
answer. Each question carries 4 marks for correct answer and –1 mark for wrong answer.
(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out
of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks
for correct answer and –1 mark for wrong answer. For Section-B, the answer should be
rounded off to the nearest integer.
MATHEMATICS
SECTION - A
Multiple Choice Questions: This section contains 20
multiple choice questions. Each question has 4 choices
(1), (2), (3) and (4), out of which ONLY ONE is correct.
Choose the correct answer:
1. The number of symmetric matrices of order 3, with
all the entries from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
is
(1) 6
10
(2) 10
6
(3) 9
10
(4) 10
9
Answer (2)
Sol. A = {0, 1, 2, 3, …8, 9}
* * *
0 **
00 *
M
??
??
=
??
??
??
? Total symmetric matrix = 10
6
2. Let
13
1 2 3 , 2
4
B
? ??
??
= ? ?
??
?? ??
??
be the adjoint of a matrix A
and |A| = 2. Then ? ? 2 2 B
? ??
??
? - ? ? - ?
??
?? ?
??
is equal to
(1) 0 (2) 16
(3) –16 (4) 32
Answer (3)
Sol.
3 1
3 1 2 , 2
4
B
??
?
??
= ? ?
??
??
??
??
And adj (A) = B, |A| = 2
? |adj (A)| = |B|
? 2
2
= (8 – 3?) – 3(4 – 3?) + ?(–?)
? ?
2
– 6? + 8 = 0
? (? – 4) (? – 2) = 0
? = 4, 2 but ? > 2 so 4 ?=
Now
? ? ? ?
3 14 4
3 2 2 4 8 4 1 2 8
444 4
B
?? ? ? ? ?
?
?? ? ? ? ?
? - ? ? - ? = - -
?? ? ? ? ?
?? ? ? ? ?
?
? ? ? ? ??
? ?
4
12 12 8 8
4
??
??
=-
??
??
??
? ? 48 96 32 16 - + = -
3. Among
( ) ( )
2
1
1 : lim 2 4 6 ... 2 1
n
Sn
n
??
+ + + + =
( )
( )
15 15 15 15
16
11
2 : lim 1 2 3 ...
16 n
Sn
n
??
+ + + + =
(1) Both (S1) and (S2) are true
(2) Only (S1) is true
(3) Both (S1) and (S2) are false
(4) Only (S2) is true
Answer (1)
Sol.
? ?
1
2
1
: lim 2 4 6 ... 2
n
Sn
n
??
+ + + +
( )
2
1
lim 2 1
2
n
nn
n
??
+
=
( )
15 15 15 15
2
16
1
: lim 1 2 3 ...
n
Sn
n
??
+ + + +
?
1
1
1
lim
1
n
k
r
k
n
r
k
n
=
+
??
=
+
?
Hence k = 15
?
15
1
16
1
lim
16
n
r
n
r
n
=
??
=
?
? Both S1 and S2 are correct
4. Fractional part of the number
2022
4
15
is equal to
(1)
8
15
(2)
4
15
(3)
14
15
(4)
1
15
Answer (4)
Sol.
2022
4
15
4 4 (mod 15) ?
2
4 1(mod 15) ?
2022
4 1(mod 15) ?
? Fractional part of
2022
41
15 15
=
5.
0
1
max 2sin cos sin3
3 x
x x x x
? ??
??
- + =
??
??
(1)
2 3 3
6
? + -
(2) ?
(3) 0 (4)
5 2 3 3
6
? + +
Answer (4)
Sol. ( ) 1 2cos2 cos3 f x x x ? = - +
( ) 4sin2 3sin3 f x x x ??=-
( ) 0 fx ? =
( )
23
1 2 2cos 1 4cos 3cos 0 x x x ? - - + - =
( )( )
( ) 2cos 3 2cos 3 cos 1 0 x x x + - - =
– 3 3
cos , , 1
22
x =
5
, , 0
66
x
??
=
5
2 3 3 0
6
f
? ??
?? = - - ?
??
??
2 3 3 0
6
f
? ??
?? = - ?
??
??
(0) 0 f ?? =
So
5
6
x
?
= is local maxima point
Maximum value of
5 5 3 1
()
6 6 2 3
f x f
?? ??
= = + +
??
??
5 2 3 3
6
? + +
=
6. The negation of the statement ( ) ( ( ) A B C ??
( )) A B A ? ? ? is
(1) equivalent to ~ C
(2) equivalent to ~ BC ?
(3) a fallacy
(4) equivalent to ~ A
Answer (4)
Sol. ( ) ( ) ( ) A B C A B A ? ? ? ? ?
( ) ( ) ( ) ( )
~~ A B C A B A ? ? ? ? ?
( ) ( ) ( ) ~ A B C A B A ? ? ? ? ?
= A
? Negation of statement = ~A
7. For , x ? two real valued functions () fx and () gx
are such that, ( ) 1 g x x =+ and
( ) 3 fog x x x = + - . Then (0) f is equal to
(1) 1 (2) 5
(3) 0 (4) –3
Answer (2)
Sol. ( ) ( )
3 f g x x x = + -
( )
13 f x x x + = + -
Put 1 xt +=
1 xt =-
x = (t – 1)
2
f(t) = (t – 1)
2
+ 3 – (t – 1)
f(0) = 1 + 3 + 1 = 5
8. Let
1 2 3 10
, , ...., s s s s respectively be the sum of 12
terms of 10 A.Ps whose first terms are 1, 2, 3,....,10
and the common differences are 1, 3, 5,...,19
respectively. Then
10
1
i
i
s
=
?
is equal to
(1) 7220
(2) 7360
(3) 7260
(4) 7380
Answer (3)
Sol. 1 10 r ??
( )( ) ( )
12
2 12 1 2 1 6 2 22 11
2
i
S r r r r ?? = + - - = + -
??
= 6(24r – 11)
( ) ? ?
10 10
11
10
6 24 11 6 24 11 240 11
2
r
rr
Sr
==
= - = ? - + -
??
= 30 (242) = 7260
9. Let the equation of plane passing through the line
of intersection of the planes 22 x y az + + = and
3 x y z - + = be 5 11 6 1 x y bz a - + = - . For c ? ,
if the distance of this plane from the point ( , , ) a c c -
is
2
,
a
then
ab
c
+
is equal to
(1) 2 (2) 4
(3) – 4 (4) – 2
Answer (3)
Sol. Let the equation of plane passing through the
intersection of two given planes:
x + 2y + az – 2 + ?(x – y + z – 3) = 0
? x(? + 1) + y(2 – ?) + z(a + ?) –2 –3? = 0
This is same as 5x –11y + bz = 6a – 1
1 2 2 3
5 11 6 1
a
ba
? + - ? + ? + ?
= = =
--
? –11? – 11 = 10 – 5?
?
7
6 21
2
-
? = - ? ? =
7 21
22
2 2 3
22
11 6 1 11 6 1 aa
+-
- ? + ?
= ? =
- - - -
?
( )
1 17
6 1 17 3
2 2 6 1
aa
a
-
- = ? - = ? =
-
7
3
21
2
11 2
a
bb
-
- ? + ?
= ? - =
-
?
1
1
22
b
b - = - ? =
? point (a, – c, c) ? (3, – c, c)
Distance
22
3 a
==
Plane: 5x – 11y + z = 17
15 11 17 2
147 3
cc + + -
=
? |12c – 2| = 14
? c = – 1,
4
3
c = – 1 ( ) c ?
?
31
4
1
ab
c
++
= = -
-
10. Let PQ be a focal chord of the parabola
2
36 yx =
of length 100, making an acute angle with the
positive x-axis. Let the ordinate of P be positive and
M be the point on the line segment PQ such that
PM : MQ = 3 : 1. Then which of the following points
does NOT lie on the line passing through M and
perpendicular to the line PQ?
(1) ( 6, 45) - (2) (6, 29)
(3) (3, 33) (4) ( 3, 43) -
Answer (4)
Sol.
Length of focal chord at ( )
2
1
100 t a t
t
??
= + =
??
??
Where a = 9
1 10
3
t
t
+ = ?
?
11
3, , 3,
33
t
-
=-
Since ordinate of P is +ve
? t = 3 or
1
3
(t = 3 as slope of PQ is positive)
? M(21, 9)
Required line : ( )
80
9 21
60
yx
-
- = -
? 4x + 3y = 111
(–3, 43) does not lie on line
? Option (4) is correct.
11. Let
ˆ ˆ ˆ ˆ ˆ ˆ
4 2 , 3 2 7 a i j k b i j k and
ˆ ˆ ˆ
24 c i j k . If a vector d satisfies
d b c b and 24 da , then
2
d is equal to
(1) 323
(2) 423
(3) 313
(4) 413
Answer (4)
Sol. d b c b ? = ?
?
( )
0 d c b - ? =
? d c b - = ?
( )
as d c c a b ? ? =
? d c b = + ?
24 ad ?= (given)
24 a c b a ? + ? ? =
? 6 + ?(3 – 8 + 14) = 24
? 9? = 18
? ? = 2
? 2 d c b =+
ˆ
8 5 18 i j k = - +
2
64 25 324 d = + +
= 413
? Option (4) is correct.
12. A coin is biased so that the head is 3 times as likely
to occur as tail. This coin is tossed until a head or
three tails occur. If X denotes the number of tosses
of the coin, then the mean of X is
(1)
37
16
(2)
15
16
(3)
21
16
(4)
81
64
Answer (3)
Sol. P(H) = 3P(T)
? ( ) ( )
31
,
44
P H P T ==
Since coin is tossed till either 1H or 3T occurs. So,
process will end in the maximum of 3 throws.
Xi 1 2 3
P(Xi)
3
4
13
44
?
1 1 1 1 1 3
4 4 4 4 4 4
? ? + ? ?
Mean
3 3 1
1 2 3
4 16 16
= ? + ? + ?
21
16
=
Option (3) is correct.
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