CBSE Class 12 Mathematics 2025 — Set 65/4/1

If M and N are square matrices of order 3 such that det(M) = m and MN = mI, then det(N) is equal to : (A) -1 (B) 1 (C) -m² (D) m²

If f(x) = 3x - 2, 0 < x ≤ 1 \2x² + ax, 1 < x < 2 is continuous for x ∈ (0, 2), then a is equal to : (A) -4 (B) -(7)/(2) (C) -2 (D) -1

If f : N → W is defined as f(n) = (n)/(2), if n is even \0, if n is odd , then f is : (A) injective only (B) surjective only (C) a bijection (D) neither surjective nor injective

The matrix 0 1 -2 \-1 0 -7 \2 7 0 is a : (A) diagonal matrix (B) symmetric matrix (C) skew symmetric matrix (D) scalar matrix

If the sides AB and AC of triangle ABC are represented by vectors hatj + hatk and 3hati - hatj + 4hatk respectively, then the length of the median through A on BC is : (A) 2√(2) units (B) √(18) units (C) frac√(34)2 units (D) frac√(48)2 units

The function f defined by f(x) = x, if x ≤ 1 \5, if x > 1 is not continuous at : (A) x = 0 (B) x = 1 (C) x = 2 (D) x = 5

If f(x) = 2x + cos x, then f(x) : (A) has a maxima at x = π (B) has a minima at x = π (C) is an increasing function (D) is a decreasing function

∫ (cos 2x - cos 2α)/(cos x - cos α) dx is equal to : (A) 2(sin x + x cos α) + C (B) 2(sin x - x cos α) + C (C) 2(sin x + 2x cos α) + C (D) 2(sin x + sin α) + C

The value of ∫₀¹ frac1ex + e-x dx is : (A) -(π)/(4) (B) (π)/(4) (C) tan⁻¹ e - (π)/(4) (D) tan⁻¹ e

The order and degree of the differential equation ((d²y)/(dx²))² + ((dy)/(dx))² = x sin((dy)/(dx)) are : (A) order 2, degree 2 (B) order 2, degree 1 (C) order 2, degree not defined (D) order 1, degree not defined

The area of the region enclosed by the curve y = √(x) and the lines x = 0 and x = 4 and x-axis is : (A) (16)/(9) sq. units (B) (32)/(9) sq. units (C) (16)/(3) sq. units (D) (32)/(3) sq. units

The corner points of the feasible region of a Linear Programming Problem are (0, 2), (3, 0), (6, 0), (6, 8) and (0, 5). If Z = ax + by; (a, b > 0) be the objective function, and maximum value of Z is obtained at (0, 2) and (3, 0), then the relation between a and b is : (A) a = b (B) a = 3b (C) b = 6a (D) 3a = 2b

Assertion (A) : If A and B are two events such that P(A ∩ B) = 0, then A and B are independent events. Reason (R) : Two events are independent if the occurrence of one does not affect the occurrence of the other. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : If the feasible region is empty in a Linear Programming Problem (LPP), then the LPP has no solution. Reason (R) : Feasible region is the region in which all the constraints are satisfied. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.

Let A and B be two square matrices of order 3 such that det(A) = 3 and det(B) = -4. Find the value of det(-6AB).

(a) Find the least value of 'a' for which f(x) = 2x² - ax + 3 is an increasing function on [2, 4]. OR (b) If f(x) = x + (1)/(x), x ≥ 1, then show that f is an increasing function.

(a) Write sin⁻¹(fracx√(1+x²)) in the simplest form. OR (b) Find the domain of sin⁻¹√(x-1).

Calculate the area of the region bounded by the curve (x²)/(9) + (y²)/(4) = 1 and the x-axis using integration.

For the curve y = 5x - 2x³, if x increases at the rate of 2 units/s, then how fast is the slope of the curve changing when x = 2 ?

(a) If f : R^+ → R is defined as f(x) = loga x (a > 0 and a ≠ 1), prove that f is a bijection. (R^+ is a set of all positive real numbers.) OR (b) Let A = \1, 2, 3\ and B = \4, 5, 6\. A relation R from A to B is defined as R = \(x, y) : x + y = 6, x ∈ A, y ∈ B\. (i) Write all elements of R. (ii) Is R a function ? Justify. (iii) Determine domain and range of R.

(a) Find k so that f(x) = (x² - 2x - 3)/(x+1), x ≠ -1 k, x = -1 is continuous at x = -1. OR (b) Check the differentiability of function f(x) = x|x| at x = 0.

Evaluate : ∫π/2π ex ((1-sin x)/(1-cos x)) dx

Find the distance of the point (-1, -5, -10) from the point of intersection of the lines (x-1)/(2) = (y-2)/(3) = (z-3)/(4) and (x-4)/(5) = (y-1)/(2) = z.

Solve the following Linear Programming Problem using graphical method : Maximise Z = 100x + 50y subject to the constraints 3x + y ≤ 600 x + y ≤ 300 y ≤ x + 200 x ≥ 0, y ≥ 0

If A is a 3 × 3 invertible matrix, show that for any scalar k ≠ 0, (kA)⁻¹ = (1)/(k)A⁻¹. Hence calculate (3A)⁻¹, where A = 2 -1 1 \-1 2 -1 \1 -1 2 .

The relation between the height of the plant (y cm) with respect to exposure to sunlight is governed by the equation y = 4x - (1)/(2)x², where x is the number of days exposed to sunlight. (i) Find the rate of growth of the plant with respect to sunlight. (ii) In how many days will the plant attain its maximum height ? What is the maximum height ?

(a) Find : ∫ (cos x)/((4+sin² x)(5-4cos² x)) dx OR (b) Evaluate : ∫₀^π (dx)/(a² cos² x + b² sin² x)

(a) Show that the area of a parallelogram whose diagonals are represented by veca and vecb is given by (1)/(2)|veca × vecb|. Also find the area of a parallelogram whose diagonals are 2hati - hatj + hatk and hati + 3hatj - hatk. OR (b) Find the equation of a line in vector and cartesian form which passes through the point (1, 2, -4) and is perpendicular to the lines (x-8)/(3) = (y+19)/(-16) = (z-10)/(7) and vecr = 15hati + 29hatj + 5hatk + μ(3hati + 8hatj - 5hatk).

Case Study - 1 Some students are having a misconception while comparing decimals. For example, a student may mention that 78.56 > 78.9 as 7856 > 789. In order to assess this concept, a decimal comparison test was administered to the students of class VI through the following question : In the recently held Sports Day in the school, 5 students participated in a javelin throw competition. The distances to which they have thrown the javelin are shown below in the table : | Name of student | Distance of javelin (in meters) | | --- | --- | | Ajay | 47.7 | | Bijoy | 47.07 | | Kartik | 43.09 | | Dinesh | 43.9 | | Devesh | 45.2 | The students were asked to identify who has thrown the javelin the farthest. Based on the test attempted by the students, the teacher concludes that 40% of the students have the misconception in the concept of decimal comparison and the rest do not have the misconception. 80% of the students having misconception answered Bijoy as the correct answer in the paper. 90% of the students who are identified with not having misconception, did not answer Bijoy as their answer. On the basis of the above information, answer the following questions : (i) What is the probability of a student not having misconception but still answers Bijoy in the test ? (1) (ii) What is the probability that a randomly selected student answers Bijoy as his answer in the test ? (1) (iii) (a) What is the probability that a student who answered as Bijoy is having misconception ? (2) OR (iii) (b) What is the probability that a student who answered as Bijoy is amongst students who do not have the misconception ? (2)

Case Study - 2 An engineer is designing a new metro rail network in a city. Initially, two metro lines, Line A and Line B, each consisting of multiple stations are designed. The track for Line A is represented by l₁ : (x-2)/(3) = (y+1)/(-2) = (z-3)/(4), while the track for Line B is represented by l₂ : (x-1)/(2) = (y-3)/(1) = (z+2)/(-3). Based on the above information, answer the following questions : (i) Find whether the two metro tracks are parallel. (ii) Solar panels are to be installed on the rooftop of the metro stations. Determine the equation of the line representing the placement of solar panels on the rooftop of Line A's stations, given that panels are to be positioned parallel to Line A's track (l₁) and pass through the point (1, -2, -3). (iii) (a) To connect the stations, a pedestrian pathway perpendicular to the two metro lines is to be constructed which passes through point (3, 2, 1). Determine the equation of the pedestrian walkway. OR (iii) (b) Find the shortest distance between Line A and Line B.

Case Study - 3 During a heavy gaming session, the temperature of a student's laptop processor increases significantly. After the session, the processor begins to cool down, and the rate of cooling is proportional to the difference between the processor's temperature and the room temperature (25^° C). Initially the processor's temperature is 85^° C. The rate of cooling is defined by the equation (d)/(dt)(T(t)) = -k(T(t) - 25), where T(t) represents the temperature of the processor at time t (in minutes) and k is a constant. Based on the above information, answer the following questions : (i) Find the expression for temperature of processor, T(t), given that T(0) = 85^° C. (ii) How long will it take for the processor's temperature to reach 40^° C ? Given that k = 0.03, loge 4 = 1.3863.