# 12th Maths Paper Solutions Set 1 : CBSE All India Previous Year 2014

General Instructions:
i. All questions are compulsory.
ii. The question paper consists of 29 questions divided into three sections A, B and C. Section A comprises of 10 questions of one mark each, Section B comprises of 12 questions of four marks each, and Section C comprises of 7 questions of six marks each.
iii. All questions in section A are to be answered in one word, one sentence or as per the exact requirements of the question.
iv. There is no overall choice. However, internal choice has been provided in 4 questions of four marks each and 2 questions of six marks each. You have to attempt only one of the alternatives in all such questions.
v. Use of calculators is not permitted.
Q1 :

If R=[(x, y) : x+2y=8] is a relation on N, write the range of R.

The given relation on N is R=[(x, y) : x+2y=8].

Let us find the different integral values of y for different integral values of x.
For x = 2, y = 3
For x = 4, y = 2
For x = 6, y = 1

R = {(2, 3), (4, 2), (6, 1)}

Therefore, the range of R is {1, 2, 3}.

Q2 :

If tan-1 x+tan-1 y=π4, xy <</span> 1, then write the value of x+y+xy.

Here, tan-1 x+tan-1 y=π4, xy <</span> 1.
tan-1(x+y1-xy)=π4
x+y1-xy=1
x+y=1-xy
x+y+xy=1
Therefore, the value of x + y + xy is 1.

Q3 :

If A is a square matrix, such that A2=A, then write the value of 7A-(I+A)3, where I is an identity matrix.

7A-(I+A)3=7A-[I3+A3+3â‹…I2â‹…A+3â‹…Iâ‹…A2]
=7A-(I+A3+3A+3A2)=7A-(I+A2â‹…A+3A+3A2) =7A-(I+Aâ‹…A+3A+3A)         (âˆµA2=A)=7A-(I+A2+6A) =7A-(I+A+6A) =7A-(I+7A) =7A-I-7A=-I
7A-(I+A)3=-I

Q4 :

If [x-y2x-yzw]=[-1045], find the value of x+y.

Q5 :

If [3x-274]=, find the value of x.

Q6 :

If f(x) =x0 t sin t dt, then write the value of f ' (x).

Q7 :

24 xx2 + 1dx

Q8 :

Find the value of 'p' for which the vectors 3iË† + 2jË† + 9kË† and iË† - 2pjË†+ 3kË† are parallel.

Q9 :

Find aâƒ— â‹… (bâƒ—  x câƒ— ), if aâƒ—  = 2iË† + jË† + 3kË†, bâƒ—  = -iË† + 2jË† +

Q10 :

If the Cartesian equations of a line are 3-x5 = y+47 = 2z-64, write the vector equation for the line.

Q11 :

If the function f : R â†’ R be given by f[x] = x2 + 2 and g : R ​â†’ R be given by g(x)=xx-1, x1, find fog and gof and hence find fog (2) and gof (-3).

Q12 :

Prove that
tan-1 [1+xâˆš-1-xâˆš1+xâˆš+1-xâˆš]=π4-12 cos-1x, -12âˆš

Q13 :

Using properties of determinants, prove that

âˆ£âˆ£âˆ£âˆ£x+y5x+4y10x+8yx4x8xx2x3xâˆ£âˆ£âˆ£âˆ£=x3

Q14 :

Find the value of dydx at Î¸=π4 if x = aeÎ¸ (sin Î¸ - cos Î¸) and y = aeÎ¸ (sin Î¸ + cos Î¸).

Q15 :

If y = P eax + Q ebx, show that

d2ydx2-(a+b)dydx+aby=0.

Q16 :

Find the value(s) of x for which y = [x(x - 2)]2 is an increasing function.

OR

Find the equations of the tangent and normal to the curve x2a2-y2b2=1 at the point (2âˆša,b).

Q17 :

Evaluate :
0π4x sin x1+cos2 x dx

OR

Evaluate :
x+2x2+5x+6âˆš dx

Q18 :

Find the particular solution of the differential equation dydx = 1 + x + y + xy, given that y = 0 when x = 1.

Q19 :

Solve the differential equation (1 + x2) dydx+y=etan-1x.

Q20 :

Show that the four points A, B, C and D with position vectors 4iË†+5jË†+kË†, -jË†-kË†, 3iË†+9jË†+4kË† and 4(-iË†+jË†+kË†), respectively, are coplanar.

OR

The scalar product of the vector

Q21 :

A line passes through (2, -1, 3) and is perpendicular to the lines râƒ— =(iË†+jË†-kË†)+Î»(2iË†-2jË†+kË†) and râƒ— =(2iË†-jË†-3kË†

Q22 :

An experiment succeeds thrice as often as it fails. Find the probability that in the next five trials, there will be at least 3 successes.

Q23 :

Two schools A and B want to award their selected students on the values of sincerity, truthfulness and helpfulness. School A wants to award Rs x each, Rs y each and Rs z each for the three respective values to 3, 2 and 1 students, respectively with a total award money of Rs 1,600. School B wants to spend Rs 2,300 to award 4, 1 and 3 students on the respective values (by giving the same award money to the three values as before). If the total amount of award for one prize on each value is Rs 900, using matrices, find the award money for each value. Apart from these three values, suggest one more value which should be considered for an award.

Q24 :

Show that the altitude of a right circular cone of maximum volume that can be inscribed in a sphere of radius r is 4r3. Also, show that the maximum volume of the cone is 827 of the volume of the sphere.

Q25 :

Evaluate:
1cos4x+sin4xdx

Q26 :

Using integration, find the area of the region bounded by the triangle whose vertices are (−1, 2), (1, 5) and (3, 4).

Q27 :

Find the equation of the plane through the line of intersection of the planes x + y + z = 1 and 2x + 3y + 4z = 5 which is perpendicular to the plane x - y + z = 0. Also find the distance of the plane, obtained above, from the origin.

OR

Find the distance of the point (2, 12, 5) from the point of intersection of the line râƒ— =2iË†-4jË†+2kË†+Î»(3iË†+4jË†+2kË†) and the plane râƒ— .(iË†-2jË†+kË†

Q28 :

A manufacturing company makes two types of teaching aids A and B of Mathematics for class XII. Each type of A requires 9 labour hours for fabricating and 1 labour hour for finishing. Each type of B requires 12 labour hours for fabricating and 3 labour hours for finishing. For fabricating and finishing, the maximum labour hours available per week are 180 and 30, respectively. The company makes a profit of Rs 80 on each piece of type A and Rs 120 on each piece of type B. How many pieces of type A and type B should be manufactured per week to get maximum profit? Make it as an LPP and solve graphically. What is the maximum profit per week?

Q29 :

There are three coins. One is a two-headed coin (having head on both faces), another is a biased coin that comes up heads 75% of the times and the third is also a biased coin that comes up tails 40% of the time. One of the three coins is chosen at random and tossed and it shows heads. What is the probability that it was the two-headed coin?

OR

Two numbers are selected at random (without replacement) from the first six positive integers. Let X denote the larger of the two numbers obtained. Find the probability distribution of the random variable X and hence, find the mean of the distribution.