Page 1
CBSE XI | Mathematics
Sample Paper – 8 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 8 Solution
SECTION – A
1.
? ? ? ?
2
1
x
2
1
x
2
1
x
2
4x 1
lim
2x 1
2x 1 2x 1
lim
2x 1
lim 2x 1 2x 1 0
2
?
?
?
?
?
??
?
?
? ? ? ?
?
2. The number 2 is not greater than 7.
OR
The number 2 is less than or equal to 7.
OR
It is false that the number 2 is greater than 7.
3.
2
1 1 i i i
i
i i i 1 i
? ? ? ?
? ? ? ? ?
?
OR
z = 1 – 3i
Comparing with a + bi we get a = 1 and b = -3
? ?
2
2
z 1 3 10 ? ? ? ?
4. Variance = 4
Standard deviation = vVariance
Standard deviation = v4
Standard deviation = 2
Page 2
CBSE XI | Mathematics
Sample Paper – 8 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 8 Solution
SECTION – A
1.
? ? ? ?
2
1
x
2
1
x
2
1
x
2
4x 1
lim
2x 1
2x 1 2x 1
lim
2x 1
lim 2x 1 2x 1 0
2
?
?
?
?
?
??
?
?
? ? ? ?
?
2. The number 2 is not greater than 7.
OR
The number 2 is less than or equal to 7.
OR
It is false that the number 2 is greater than 7.
3.
2
1 1 i i i
i
i i i 1 i
? ? ? ?
? ? ? ? ?
?
OR
z = 1 – 3i
Comparing with a + bi we get a = 1 and b = -3
? ?
2
2
z 1 3 10 ? ? ? ?
4. Variance = 4
Standard deviation = vVariance
Standard deviation = v4
Standard deviation = 2
CBSE XI | Mathematics
Sample Paper – 8 Solution
SECTION – B
5. According to the question,
A n B = {b, d}
n(A n B) = 2
n(A’ ? B’) = n(A n B)’ = n(A ? B) – n(A n B) = 8 – 2 = 6
6. f
-1
(-5) = x. Then,
f(x) = -5
x
2
+ 1 = -5
x
2
= -6
This equation is not solvable in R. Therefore, there is no pre-image of -5.
Hence, f
-1
(-5) = ?
OR
f(x) =
x1
x1
?
?
1
1
1
x
f
1
x
1
x
?
??
?
??
??
?
1 1 x
f
x 1 x
? ??
?
??
?
??
? ? x1
1
f
x x 1
??
??
?
??
?
??
? ?
1
f f x
x
??
??
??
??
7. 30’’ =
''
30 1
60 2
? ? ? ?
?
? ? ? ?
? ? ? ?
37’ 30’’ =
''
1 75 75 1 5
37
2 2 2 60 8
??
? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
OR
Let s be the length of the arc subtending an angle ?
c
at the centre of a circle of radius r.
s = r? here r = 5 cm and ? = 15°
5
s r 5 15
180 12
??
? ? ? ? ? ?
Page 3
CBSE XI | Mathematics
Sample Paper – 8 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 8 Solution
SECTION – A
1.
? ? ? ?
2
1
x
2
1
x
2
1
x
2
4x 1
lim
2x 1
2x 1 2x 1
lim
2x 1
lim 2x 1 2x 1 0
2
?
?
?
?
?
??
?
?
? ? ? ?
?
2. The number 2 is not greater than 7.
OR
The number 2 is less than or equal to 7.
OR
It is false that the number 2 is greater than 7.
3.
2
1 1 i i i
i
i i i 1 i
? ? ? ?
? ? ? ? ?
?
OR
z = 1 – 3i
Comparing with a + bi we get a = 1 and b = -3
? ?
2
2
z 1 3 10 ? ? ? ?
4. Variance = 4
Standard deviation = vVariance
Standard deviation = v4
Standard deviation = 2
CBSE XI | Mathematics
Sample Paper – 8 Solution
SECTION – B
5. According to the question,
A n B = {b, d}
n(A n B) = 2
n(A’ ? B’) = n(A n B)’ = n(A ? B) – n(A n B) = 8 – 2 = 6
6. f
-1
(-5) = x. Then,
f(x) = -5
x
2
+ 1 = -5
x
2
= -6
This equation is not solvable in R. Therefore, there is no pre-image of -5.
Hence, f
-1
(-5) = ?
OR
f(x) =
x1
x1
?
?
1
1
1
x
f
1
x
1
x
?
??
?
??
??
?
1 1 x
f
x 1 x
? ??
?
??
?
??
? ? x1
1
f
x x 1
??
??
?
??
?
??
? ?
1
f f x
x
??
??
??
??
7. 30’’ =
''
30 1
60 2
? ? ? ?
?
? ? ? ?
? ? ? ?
37’ 30’’ =
''
1 75 75 1 5
37
2 2 2 60 8
??
? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
OR
Let s be the length of the arc subtending an angle ?
c
at the centre of a circle of radius r.
s = r? here r = 5 cm and ? = 15°
5
s r 5 15
180 12
??
? ? ? ? ? ?
CBSE XI | Mathematics
Sample Paper – 8 Solution
8. B – C = {2, 3, 6} – {2, 3, 7} = {6}
A × (B – C) = {1, 4} × {6} = {(1, 6), (4, 6)}…….(i)
A × B = {1, 4} × {2, 3, 6} = {(1, 2), (1, 3), (1, 6), (4, 2), (4, 3), (4, 6)}
A × C = {1, 4} × {2, 3, 7} = {(1, 2), (1, 3), (1, 7), (4, 2), (4, 3), (4, 7)}
A × B – A × C = {(1, 6), (4, 6)}…..(ii)
From (i) and (ii)
A × (B – C) = A × B – A × C
9. sin
2
x + sin x – 2 = 0
(sinx + 2)(sinx – 1) = 0
Sin x + 2 = 0 or sin x – 1 = 0
sin x = -2 or sin x = 1
sin x cannot be -2 hence, sin x = 1.
x = 90°
OR
22
2
2
tan tan
4 2 4 2
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
2 1 tan
2
1 tan
2
2
cos
2sec
? ? ? ? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
??
??
??
??
??
?? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
?
?? ? ? ? ?
??
? ? ? ?
? ? ? ?
? ??
?
??
??
?
?
?
?
?
??
10. The compound statement is “25 is a multiple of 5 or 8”.
Let us assume that the statement q is false i. e. 25 is not a multiple of 8. Clearly p is true.
Thus, if we assume that q is false then p is true. Hence, compound statement is true.
Page 4
CBSE XI | Mathematics
Sample Paper – 8 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 8 Solution
SECTION – A
1.
? ? ? ?
2
1
x
2
1
x
2
1
x
2
4x 1
lim
2x 1
2x 1 2x 1
lim
2x 1
lim 2x 1 2x 1 0
2
?
?
?
?
?
??
?
?
? ? ? ?
?
2. The number 2 is not greater than 7.
OR
The number 2 is less than or equal to 7.
OR
It is false that the number 2 is greater than 7.
3.
2
1 1 i i i
i
i i i 1 i
? ? ? ?
? ? ? ? ?
?
OR
z = 1 – 3i
Comparing with a + bi we get a = 1 and b = -3
? ?
2
2
z 1 3 10 ? ? ? ?
4. Variance = 4
Standard deviation = vVariance
Standard deviation = v4
Standard deviation = 2
CBSE XI | Mathematics
Sample Paper – 8 Solution
SECTION – B
5. According to the question,
A n B = {b, d}
n(A n B) = 2
n(A’ ? B’) = n(A n B)’ = n(A ? B) – n(A n B) = 8 – 2 = 6
6. f
-1
(-5) = x. Then,
f(x) = -5
x
2
+ 1 = -5
x
2
= -6
This equation is not solvable in R. Therefore, there is no pre-image of -5.
Hence, f
-1
(-5) = ?
OR
f(x) =
x1
x1
?
?
1
1
1
x
f
1
x
1
x
?
??
?
??
??
?
1 1 x
f
x 1 x
? ??
?
??
?
??
? ? x1
1
f
x x 1
??
??
?
??
?
??
? ?
1
f f x
x
??
??
??
??
7. 30’’ =
''
30 1
60 2
? ? ? ?
?
? ? ? ?
? ? ? ?
37’ 30’’ =
''
1 75 75 1 5
37
2 2 2 60 8
??
? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
OR
Let s be the length of the arc subtending an angle ?
c
at the centre of a circle of radius r.
s = r? here r = 5 cm and ? = 15°
5
s r 5 15
180 12
??
? ? ? ? ? ?
CBSE XI | Mathematics
Sample Paper – 8 Solution
8. B – C = {2, 3, 6} – {2, 3, 7} = {6}
A × (B – C) = {1, 4} × {6} = {(1, 6), (4, 6)}…….(i)
A × B = {1, 4} × {2, 3, 6} = {(1, 2), (1, 3), (1, 6), (4, 2), (4, 3), (4, 6)}
A × C = {1, 4} × {2, 3, 7} = {(1, 2), (1, 3), (1, 7), (4, 2), (4, 3), (4, 7)}
A × B – A × C = {(1, 6), (4, 6)}…..(ii)
From (i) and (ii)
A × (B – C) = A × B – A × C
9. sin
2
x + sin x – 2 = 0
(sinx + 2)(sinx – 1) = 0
Sin x + 2 = 0 or sin x – 1 = 0
sin x = -2 or sin x = 1
sin x cannot be -2 hence, sin x = 1.
x = 90°
OR
22
2
2
tan tan
4 2 4 2
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
2 1 tan
2
1 tan
2
2
cos
2sec
? ? ? ? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
??
??
??
??
??
?? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
?
?? ? ? ? ?
??
? ? ? ?
? ? ? ?
? ??
?
??
??
?
?
?
?
?
??
10. The compound statement is “25 is a multiple of 5 or 8”.
Let us assume that the statement q is false i. e. 25 is not a multiple of 8. Clearly p is true.
Thus, if we assume that q is false then p is true. Hence, compound statement is true.
CBSE XI | Mathematics
Sample Paper – 8 Solution
11. The values of x for which f(x) and g(x) are equal given by
f(x) = g(x)
2x
2
– 1 = 1 – 3x
2x
2
+ 3x – 2 = 0
(x + 2) (2x – 1) = 0
x = -2, ½
Thus, f(x) and g(x) are equal on the set {-2, ½}.
12. Suppose the line x + y = 4 divides the join of A(-1, 1) and B(5, 7) in the ratio k : 1.
The coordinate of the point of division are
5k 1 7k 1
,
k 1 k 1
?? ??
??
??
??
It lies on x + y = 4.
5k 1 7k 1
4
k 1 k 1
??
??
??
5k – 1 + 7k + 1 = 4k + 4
12k – 4k = 4
8k = 4
k = ½
SECTION – C
13.
1
1
sec8 1
cos8
1
sec4 1
1
cos4
?
??
?
?
??
?
?
? ?
? ?
1 cos8 cos4
cos8 1 cos4
? ? ?
?
? ? ?
2
2
2sin 4 cos4
cos8 2sin 2
??
?
??
2
2sin4 cos4 sin4
cos8 2sin 2
? ? ?
??
? ?
2
2sin4 cos4 2sin2 cos2
cos8 2sin 2
? ? ? ?
??
? ?
sin8 cos2
cos8 sin2
??
??
??
tan8 cot2 ? ? ? ?
tan8
tan2
?
?
?
Page 5
CBSE XI | Mathematics
Sample Paper – 8 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 8 Solution
SECTION – A
1.
? ? ? ?
2
1
x
2
1
x
2
1
x
2
4x 1
lim
2x 1
2x 1 2x 1
lim
2x 1
lim 2x 1 2x 1 0
2
?
?
?
?
?
??
?
?
? ? ? ?
?
2. The number 2 is not greater than 7.
OR
The number 2 is less than or equal to 7.
OR
It is false that the number 2 is greater than 7.
3.
2
1 1 i i i
i
i i i 1 i
? ? ? ?
? ? ? ? ?
?
OR
z = 1 – 3i
Comparing with a + bi we get a = 1 and b = -3
? ?
2
2
z 1 3 10 ? ? ? ?
4. Variance = 4
Standard deviation = vVariance
Standard deviation = v4
Standard deviation = 2
CBSE XI | Mathematics
Sample Paper – 8 Solution
SECTION – B
5. According to the question,
A n B = {b, d}
n(A n B) = 2
n(A’ ? B’) = n(A n B)’ = n(A ? B) – n(A n B) = 8 – 2 = 6
6. f
-1
(-5) = x. Then,
f(x) = -5
x
2
+ 1 = -5
x
2
= -6
This equation is not solvable in R. Therefore, there is no pre-image of -5.
Hence, f
-1
(-5) = ?
OR
f(x) =
x1
x1
?
?
1
1
1
x
f
1
x
1
x
?
??
?
??
??
?
1 1 x
f
x 1 x
? ??
?
??
?
??
? ? x1
1
f
x x 1
??
??
?
??
?
??
? ?
1
f f x
x
??
??
??
??
7. 30’’ =
''
30 1
60 2
? ? ? ?
?
? ? ? ?
? ? ? ?
37’ 30’’ =
''
1 75 75 1 5
37
2 2 2 60 8
??
? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
OR
Let s be the length of the arc subtending an angle ?
c
at the centre of a circle of radius r.
s = r? here r = 5 cm and ? = 15°
5
s r 5 15
180 12
??
? ? ? ? ? ?
CBSE XI | Mathematics
Sample Paper – 8 Solution
8. B – C = {2, 3, 6} – {2, 3, 7} = {6}
A × (B – C) = {1, 4} × {6} = {(1, 6), (4, 6)}…….(i)
A × B = {1, 4} × {2, 3, 6} = {(1, 2), (1, 3), (1, 6), (4, 2), (4, 3), (4, 6)}
A × C = {1, 4} × {2, 3, 7} = {(1, 2), (1, 3), (1, 7), (4, 2), (4, 3), (4, 7)}
A × B – A × C = {(1, 6), (4, 6)}…..(ii)
From (i) and (ii)
A × (B – C) = A × B – A × C
9. sin
2
x + sin x – 2 = 0
(sinx + 2)(sinx – 1) = 0
Sin x + 2 = 0 or sin x – 1 = 0
sin x = -2 or sin x = 1
sin x cannot be -2 hence, sin x = 1.
x = 90°
OR
22
2
2
tan tan
4 2 4 2
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
1 tan 1 tan
22
2 1 tan
2
1 tan
2
2
cos
2sec
? ? ? ? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
??
??
??
??
??
?? ? ? ? ?
? ? ?
? ? ? ?
? ? ? ?
?
?? ? ? ? ?
??
? ? ? ?
? ? ? ?
? ??
?
??
??
?
?
?
?
?
??
10. The compound statement is “25 is a multiple of 5 or 8”.
Let us assume that the statement q is false i. e. 25 is not a multiple of 8. Clearly p is true.
Thus, if we assume that q is false then p is true. Hence, compound statement is true.
CBSE XI | Mathematics
Sample Paper – 8 Solution
11. The values of x for which f(x) and g(x) are equal given by
f(x) = g(x)
2x
2
– 1 = 1 – 3x
2x
2
+ 3x – 2 = 0
(x + 2) (2x – 1) = 0
x = -2, ½
Thus, f(x) and g(x) are equal on the set {-2, ½}.
12. Suppose the line x + y = 4 divides the join of A(-1, 1) and B(5, 7) in the ratio k : 1.
The coordinate of the point of division are
5k 1 7k 1
,
k 1 k 1
?? ??
??
??
??
It lies on x + y = 4.
5k 1 7k 1
4
k 1 k 1
??
??
??
5k – 1 + 7k + 1 = 4k + 4
12k – 4k = 4
8k = 4
k = ½
SECTION – C
13.
1
1
sec8 1
cos8
1
sec4 1
1
cos4
?
??
?
?
??
?
?
? ?
? ?
1 cos8 cos4
cos8 1 cos4
? ? ?
?
? ? ?
2
2
2sin 4 cos4
cos8 2sin 2
??
?
??
2
2sin4 cos4 sin4
cos8 2sin 2
? ? ?
??
? ?
2
2sin4 cos4 2sin2 cos2
cos8 2sin 2
? ? ? ?
??
? ?
sin8 cos2
cos8 sin2
??
??
??
tan8 cot2 ? ? ? ?
tan8
tan2
?
?
?
CBSE XI | Mathematics
Sample Paper – 8 Solution
14.
1. It is a function. Because normally each country has exactly one capital city.
2. It is not a function.
For each replacement of x there are many replacements of y which makes the
sentence true.
3. It is not a function.
Each Maths teacher ordinarily has a number of pupils.
4. It is a function.
Each replacement of x gives one and only one replacement of y which makes the
sentence true.
15. (x, y) ? R ? x + 2y = 10 ? y =
10 x
2
?
, x, y ? A where A = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
x = 1 ? y = 9/2 ? A
This shows that 1 is not related to any element in A. Similarly we can observe that 3, 5,
7, 9 and 10 are not related to any element of A under the defined relation.
Further we find that
For x = 2, y = 4 ? A therefore, (2, 4) ? R
For x = 4, y = 3 ? A therefore, (4, 3) ? R
For x = 6, y = 2 ? A therefore, (6, 2) ? R
For x = 8, y = 1 ? A therefore, (8, 1) ? R
Thus, R = {(2, 4), (4, 3), (6, 2), (8, 1)} ? R
-1
= {(4, 2), (3, 4), (2, 6), (1, 8)}
Clearly, Dom(R) = {2, 4, 6, 8} = Range R
-1
and Range (R) = {4, 3, 2, 1} = Dom (R
-1
)
16. log10 2, log10 (2
x
– 1) and log10 (2
x
+ 3) are in A. P.
2log10 (2
x
– 1) = log10 2 + log10 (2
x
+ 3)
log10 (2
x
– 1)
2
= log10 [2(2
x
+ 3)]
(2
x
– 1)
2
= 2(2
x
+ 3)
(y – 1)
2
= 2(y + 3) ? y = 2
x
y
2
– 2y + 1 = 2y + 6
y
2
– 4y – 5 = 0
(y – 5)(y + 1) = 0
Y = 5, -1
When y = 5, then 2
x
= 5 ? x = log2 5
When y = -1 then 2
x
= -1 which is impossible.
Hence, x = log2 5
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