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Question 1. There are 5 girls and 7 boys. A team of 3 boys and 2 girls is to be formed such that no two specific boys are in the same team. Number of way to do so
Solution:
Total number of teams = 7C3× 5C2
= 35×10 = 350
Let A, B be the specific boys.
Number of teams with these two boys in the same team = 5C1 × 5C2
= 5×10 = 50
Required number of ways = 350-50 = 300
Answer:(d)
Question 2. The equation x2+2x+2 = 0 has roots α and β. Then value of α15 + β15is;
Solution:
Solution:
(x+1)2 = -1 ⇒ x+1 = ±i
x = -1+I, -1-i
α = -1+I, β = -1-i
α = √2ei(3π/4), β = √2ei(-3π/4)
α15+ β15 = (√2)15(ei(45π/4) + ei(-45π/4))
= 215/2(2 cos(45π/4))
= 215/2 (2×-1/√2)
= -28
= -256
Answer: (d)
Question 3.
Solution:
Answer: (a)
Question 4. If x2 ≠ nπ+1, n ∈N, then
Solution:
Let x2-1 = t
2x dx = dt
x dx = dt/2
=
=
=
Answer: (c)
Question 5. If
Solution:
From (i), (ii) and (iii)
Answer: (c)
Question 6.If
then:
Solution:
f(1-) = f(1+)
a+b = 5 ..(i)
f(3+) = f(3-)
b+15 = a+3b ..(ii)
f(5+) = f(5-)
b + 25 = 30 … (iii)
From (iii), b = 5
From (i), a = 0 & from (ii), a = 5
f ( x) is discontinuous ∀a ∈R, b∈ R
Answer: (a)
Question 7. Average height and variance of 5 students in a class is 150 and 18 respectively. A new student whose height is 156 cm is added to the group. Find new variance.
Solution:
Let 5 students are x1 , x2 , x3 , x4 , x5
Given
Ʃxi = 750 ..(i)
Height of new student = 156 (Let x6)
Now x1+ x2+ x3+x4 +x5+x6 = 750+156
Variance (new) =
= [(x12 + x22+ x32+ x42+ x52+ x62)/6]-(151)2
From equation (2) and (3)
Var(new) = [112590+(156)2/6] - (151)2
= 22821 - 22801
= 20
Answer: (a)
Question 8. a,b,c are in G.P. a+b+c = bx , then x cannot be;
Solution:
Let the terms of G.P be a/r, a, ar
(a/r) + a+ar = ax
x = r+(1/r)+1
But r+(1/r) ≥ 2
Or r+(1/r) ≤ -2 ( using A.M,G.M inequality )
x-1 ) ≥ 2 or x-1 ≤ -2
x ≥ 3 or x ≤ -1
So x cannot be 2.
Answer: (a)
Question 9.{2403/15} = k/15 then find k. (where {.} denotes fractional part function).
Solution:
Solution:
24 ≡ 1 (mod 15)
2400 ≡ 1 (mod 15)
2403 ≡ 8(mod 15)
{2403/15} = 8/15
k = 15
Answer: (b)
Question 10.
Solution:
Rationalising numerator,
Answer: (a)
Question 11.There is a parabola having axis as x-axis, vertex is at a distance of 2 unit from origin & focus is at (4, 0). Which of the following point does not lie on the parabola.
Solution:
The equation of parabola is y2 = 8(x-2)
(6,8) does not lie on this curve.
Answer: (a)
Question 12. Find sum of all possible values of θ in the interval (-π/2, π) for which
Solution:
=
For z to be purely imaginary, Re(z) = 0
i.e
sin2 θ = 3/4
As θ∈ (-π/2,π ) = ±π/3, 2π/3
Sum of all values of θ = 2π/3
Answer: (c)
Question 13.Let A =
Solution:
A =
A is a rotation matrix.
An =
A-50 =
A-50 at θ= π/2 is
=
Answer: (b)
Question 14. If (A⊕B)∧(∼ A⊝ B) =
Solution:
By inspection ⊕ represents ∧ and ⊝ represents ∨
A |
B |
A∧B |
~A |
~A∨B |
(A∧B)∧ (~A∨B) |
T |
T |
T |
F |
T |
T |
T |
F |
F |
F |
F |
F |
F |
T |
F |
T |
T |
F |
F |
F |
F |
T |
T |
F |
(A∧B)∧(~A∨B)≡ A∧B
Answer: (a)
Question 15. If y (x) is solution of x(dy/dx) +2y = x2, y(1) = 1, then value of y(1/2)
Solution:
x(dy/dx) + 2y = x2
(dy/dx) + 2y/x = x
This is linear differential equation.
I.F =e ∫(2/x)dx = e2 log x = x2
solution is x2y = ∫x3 dx
x2y = (x4/4) + c
y(1) = 1 c = ¾
at x = 1/2 (¼)y = (1/64) +(3/4)
y = 49/16.
Answer: (b)
Question 16. From a well shuffled deck of cards, 2 cards are drawn with replacement. If x represent numbers of times ace coming, then value of P(x = 1) + P(x = 2) is;
Solution:
P(x = 1) = 2C1×(4/52)×(48/52) = 24/169
P(x = 2) = 2C2×(4/52)2= 1/169
P(x = 1) + P(x = 2) = 25/169
Answer: (a)
Question 17. If eccentricity of the hyperbola
Solution:
For hyperbola, e2 = 1+(b2/a2)
= 1+tan2 θ
= sec2θ
e>2 ⇒ sec θ > 2
∈(π/3, π/2)
Length of latus rectum =2b2/a = 2 tan θ sin θ
= 2(>√3)(> √3/2)
> 3
Answer (a)
Question 18. If slant height of a right circular cone is 3 cm then the maximum volume of cone is
Solution:
l = 3
r2 + h2 = 9
r2 = 9 -h2
V = (1/3)πr2h
= (1/3)πh(9 -h2)
V = 3πh - 1/3πh3
For maximum volume, dv/dh = 0
3π - πh2 = 0
h2 = 3
h = √3
r2 = 6
Volume = (1/3)π (6)(√3) = 2√3 πcm3
Answer (a)
Question 19. If cos-1(2/3x) + cos-1(3/4x) = π/2, x>3/4 then x =
Solution:
cos-1 (2/3x) = π/2 - cos-1(3/4x)
cos-1 (2/3x) = cos-1 (√(16x2-9)/4x
2/3x = (√(16x2-9)/4x
(√(16x2-9) = 8/3
16x2-9 = 64/9
x2 = 145/(9×16)
x = √145/12
Answer: (b)
Question 20. If px+qy+r = 0 represent a family of straight lines such that 3p+2q+4r = 0 then;
Solution:
Px+qy+r = 0 … (i)
3p+2q+4r = 0
(3p/4) +(q/2) +r = 0 ..(ii)
(i) and (ii) are identical.
x = 3/4 and y = 1/2.
Answer: (d)
Question 21. Consider the system of equations x+y+z = 1, 2x+3y+2z =1, 2x+3y+(a2 -1)z = a+1 then
Solution:
x + y + z = 1 … (i)
2x + 3y + 2z = 1 … (ii)
2x + 3y + (a2 −1)z = a +1 …(iii)
By observation, when a2-1 = 2
LHS of (ii) & (iii) are same but RHS different
Hence a2 = 3 ⇒ ǀaǀ = √3
For ǀaǀ = √3, the system is inconsistent.
Answer: (b)
Question 22.The value of 3(cos θ - sin θ)4 + 6(sin θ + cos θ)2+4 sin6θ is, where θ∈ (π/4, π/2)
Solution:
3(cos2 θ+ sin2 θ -sin 2θ)2 +6(sin2 θ+ cos2 θ+ sin 2θ) +4sin6θ
= 3(1+sin2 2θ - 2sin 2θ)+6+6sin 2θ+4sin6θ
= 9+3sin2 2θ +4 sin6θ
= 9+3(4 sin2θ cos2θ)+4(1-cos2θ)3
= 9+12 cos2θ sin2θ+4(1-cos6θ-3 cos2θ sin2θ)
= 9+12 sin2θ cos2θ +4-4 cos6θ-12 sin2θ cos2θ)
= 13 - 4 cos6θ
Answer: (b)
Question 23. 3 circles of radii a, b, c (a < b < c) touch each other externally and have x - axis as a common tangent then;
Solution:
PQ +QR = PR
√(4ac) + √(4ab) = √(4bc)
Dividing with √(4abc)
(1/√b) + (1/√c) = (1/√a)
Answer: (a)
Question 24.If f(x) = 1/x, f2(x) = 1-x, f3(x) = 1/(1-x) then find J(x) such that f2oJof1(x) = f3(x)
Solution:
f2(J(f1(x))) = f3(x)
f2(J(1/x)) = 1/(1-x)
1-J(1/x) = 1/(1-x)
J(1/x) = 1-(1/(1-x)) = x/(x-1)
J(x) = 1/(1-x) = f3(x)
Answer: (c)
Question 25.Find the equation of line through (−4,1,3) and parallel to the plane x + y + z = 3 while the line intersects another line whose equation is x + y - z = 0 = x + 2y -3z + 5;
Solution:
Family of planes containing the line of intersection of planes is π1 +λπ2 = 0
i.e. (x +y -z) +λ(x +2y -3z +5) = 0
This is passing through (-4,1,3)
λ= -1
Hence the equation of plane is y -2z + 5 = 0
Required line is lie in this plane and is parallel to x + y + z = 5
direction of required line =
=
Required line is
Answer (c)
Question 26.Consider the curves y = x2 +2 and y = 10-x2. Let θ be the angle between both the curves at point of intersection, then find ǀtan θǀ
Solution:
x2 +2 = 10-x2
x = ±2 and y = 4
Point of intersection of curves = (±2, 4)
y = x2+2; y = 10-x2
(dy/dx) = 2x; (dy/dx) = -2x
(dy/dx) at (±2, 4) = ±4 = m1; (dy/dx) at (±2, 4) = ±4 = m2
ǀtan θǀ = ǀ8/(1-16)ǀ
= 8/15
Answer (a)
Question 27.A plane parallel to y-axis passing through line of intersection of planes x+y+z =1 and 2x+3y-z-4 = 0 which of the point lie on the plane.
Solution:
Required plane is π1+ λπ2 = 0
(x+y+z-1)+λ(2x+3y-z-4) = 0
(1+2λ)x+(1+3λ)y+(1-λ)z-(1+4λ) = 0
This is parallel to y axis ⇒ λ = -1/3
Required plane is x+4z+1 = 0
By inspection, (3,1,-1) lie in this plane.
Answer (d)
Question 28.Find common tangent of the two curves y2 = 4x and x2+y2-6x = 0.
Solution:
Equation of tangent to the parabola y2 = 4x is y = mx+(1/m)
m2x-my+1 = 0
This is also tangent to x2+y2-6x = 0.
i.e.,
9m4+1+6m2 = 9m4+9m2
3m2 = 1
m = ±1/√3
The common tangent is y = ±((x/√3)+√3)
Answer (1)
Question 29.
The area bounded by the curve y = x2 -1, tangent to it at (2, 3) and y-axis is;
Solution:
Equation of tangent at (2, 3) is
(y+3)/2 = 2x-1
y+3 = 4x-2
4x-y = 5
Required area = Ar(PAB) -
=
=
= 8-(16/3)
= 8/3
Answer (c)