MODEL PAPER OF MATHEMATICS FOR GRADE-11
FOR (ANNUAL EXAM-2027) — Objective Type
Time Allowed: 30 MinutesMaximum Marks: 20
1. Note: Four possible answers A, B, C and D to each question are given. The choice which you think is correct, fill that circle with marker or ink pen in the answer-book. Cutting or filling two or more circles will result in zero mark in that question.
i. The multiplicative identity in complex number is:
(A) (1, 1)(B) (0, 0)(C) (1, 0)(D) (0, 1)
Ans: (C) — (a,b)(1,0) = (a,b).
ii. The sum of all the three cube roots of unity is:
(A) 1(B) 2(C) 3(D) 0
Ans: (D) — 1 + ω + ω² = 0.
iii. The domain of the function f(x) =
√(4 − x²) is:
(A) (−2, 2)(B) (−2, ∞)(C) (−∞, 2)(D) [−2, 2]
Ans: (D) — 4 − x² ≥ 0 ⇒ −2 ≤ x ≤ 2.
iv. What is the maximum value of f(x) = −2x² + 4x + 3?
(A) 1(B) 3(C) 5(D) 7
Ans: (C) — vertex x = −b/2a = 1; f(1) = −2 + 4 + 3 = 5.
v. If order of matrix A is m×n and order of matrix B is n×p then order of AB is:
(A) n×p(B) m×n(C) m×p(D) p×n
Ans: (C)
vi. If C is a matrix of order 3×3 and k ∈ R is any scalar then |kC| is equal:
(A) k|C³|(B) k³|C³|(C) k³|C|(D) (kC)³
Ans: (C) — |kC| = kn|C|, n = 3.
vii. An expression of the form
p(x)q(x), q(x) ≠ 0 is called:
(A) Partial fraction(B) Rational fraction(C) Irrational fraction(D) Polynomial
Ans: (B)
viii. The Arithmetic mean between 3√3 and √3 is:
(A) 4(B) 4√3(C) 2√3(D) √3
Ans: (C) — (3√3 + √3)/2 = 2√3.
ix. The next term of the sequence 1, 3, 9, 27,… is:
(A) 30(B) 60(C) 81(D) 99
Ans: (C) — r = 3; 27 × 3 = 81.
x. 0! is equal to
(A) 0(B) 1(C) 2(D) 3
Ans: (B)
xi. The number of diagonals of 6-sided figure is:
(A) 9(B) 18(C) 20(D) 35
Ans: (A) — n(n−3)/2 = 6·3/2 = 9.
xii. The remainder when f(x) = x&sup4; + x³ + x² + 1 is divided by x + 1 is:
(A) 1(B) 2(C) 3(D) 4
Ans: (B) — f(−1) = 1 − 1 + 1 + 1 = 2.
xiii. Cosec(
π2 + α) is equal to:
(A) cosα(B) sinα(C) secα(D) cosecα
Ans: (C) — sin(π/2 + α) = cosα, so cosec = secα.
xiv. The value of cos(
π2 +
π6) is:
(A) −15(B) 12(C) −12(D) √32
Ans: (C) — cos(90° + 30°) = −sin30° = −1/2.
xv. The range of y = tan(x) is:
(A) (−∞, 0)(B) (−∞, ∞)(C) (−∞, −1) ∪ (1, ∞)(D) (−1, 1)
Ans: (B)
xvi. lim
x→a x
p is equal to:
(A) p(B) a(C) pa(D) ap
Ans: (D)
xvii. The notation used by Newton to denote derivative of y = f(x) is:
(A) dydx(B) ḟ(x)(C) f′(x)(D) Df(x)
Ans: (B) — Newton: dot notation; Leibniz: dy/dx; Lagrange: f′; Cauchy: D.
xviii. The derivative of f(x) = x² − 3 at x = 2?
(A) 4(B) 2(C) 3(D) 5
Ans: (A) — f′(x) = 2x; f′(2) = 4.
xix. Angle between vectors
p and
q, if
p·
q =
35 and |
p×
q| =
35 is:
(A) 30°(B) 45°(C) 60°(D) 90°
Ans: (B) — tanθ = |p×q| / p·q = 1 ⇒ θ = 45°.
xx. Magnitude of a vector perpendicular to both
u = 2
i − 3
j +
k and
v =
i + 4
j − 2
k is:
(A) √50(B) √150(C) √500(D) √1550
Ans: (B) — u×v = (6−4)i − (−4−1)j + (8+3)k = 2i + 5j + 11k; magnitude = √(4+25+121) = √150.
Subjective Type (Part-I)
Time allowed: 2:30 hoursMax. Marks: 80
2. Write short answers to any EIGHT (8) questions:2 × 8 = 16
(i) If z
1 = (4, 2) and z
2 = (3, −1), then find z
1/z
2.
z1/z2 = (4+2i)/(3−i) = (4+2i)(3+i)/(9+1) = (12+4i+6i−2)/10 = (10+10i)/10 = 1 + i = (1, 1).
(ii) Show that: i
n+1 + i
n+2 + i
n+3 + i
n+4 = 0, for all n ∈ N.
LHS = in+1(1 + i + i² + i³) = in+1(1 + i − 1 − i) = in+1(0) = 0 = RHS.
(iii) Find the square root of complex number 5 + 12i.
Let √(5+12i) = x+iy ⇒ x²−y² = 5, 2xy = 12. Since (x²+y²)² = 25 + 144 = 169, x²+y² = 13. So x² = 9, y² = 4. Since xy > 0: ±(3 + 2i).
(iv) If ω is an imaginary cube root of unity, prove that
a + bω² + cωaω + bω²… — i.e. (a + bω² + cω)/(aω² + bω + c) = ω.
Multiply denominator by ω: ω(aω² + bω + c) = aω³ + bω² + cω = a + bω² + cω (as ω³ = 1). Hence numerator = ω × denominator, so ratio = ω.
(v) Given f(x) = x³ − ax² + bx + 1. If f(2) = −3 and f(−1) = 0, find a and b.
f(2) = 8 − 4a + 2b + 1 = −3 ⇒ 2a − b = 6. f(−1) = −1 − a − b + 1 = 0 ⇒ a + b = 0. Adding: 3a = 6, a = 2, b = −2.
(vi) Find the domain and range of f(x) =
√(x² − 9).
x² − 9 ≥ 0 ⇒ Domain = (−∞, −3] ∪ [3, ∞). Range = [0, ∞).
(vii) Find the inverse of f(x) = 3x² − 2x + 6, x ≥ 5.
y = 3x² − 2x + 6 ⇒ 3x² − 2x + (6 − y) = 0 ⇒ x = [1 ± √(3y − 17)]/3. As x ≥ 5, take +. f−1(x) = [1 + √(3x − 17)]/3.
(viii) Solve |x² + 1| = 5.
x² + 1 > 0, so x² + 1 = 5 ⇒ x² = 4 ⇒ x = ±2.
(ix) If A and B are square matrices of the same order, explain why in general (A+B)² ≠ A² + 2AB + B².
(A+B)² = A² + AB + BA + B². Matrix multiplication is not commutative (AB ≠ BA in general), so AB + BA ≠ 2AB.
(x) Find the values of x if the determinant |2 1 x; −1 −4 −3; x 1 0| = 5.
Expand along R1: 2(0 + 3) − 1(0 + 3x) + x(−1 + 4x) = 6 − 3x − x + 4x² = 4x² − 4x + 6 = 5 ⇒ 4x² − 4x + 1 = 0 ⇒ (2x−1)² = 0 ⇒ x = ½.
(xi) If A is a square matrix of order 3, show that |kA| = k³|A|.
kA multiplies each of the 3 rows of A by k. Taking k common from each row gives k·k·k|A| = k³|A|.
(xii) Resolve
2x² − 1 into partial fractions.
2/[(x−1)(x+1)] = A/(x−1) + B/(x+1). 2 = A(x+1) + B(x−1). x = 1: A = 1; x = −1: B = −1. = 1/(x−1) − 1/(x+1).
3. Write short answers to any EIGHT (08) questions:2 × 8 = 16
(i) Which term of the A.P. 3, 8, 13, … is 123?
a = 3, d = 5: 3 + (n−1)5 = 123 ⇒ n − 1 = 24 ⇒ n = 25.
(ii) Find the sum of the first 100 positive integers.
S = n(n+1)/2 = 100×101/2 = 5050.
(iii) Find the 12th term of 1 + i, 2i, −2 + 2i, …
r = 2i/(1+i) = 1 + i (G.P.). a12 = (1+i)(1+i)11 = (1+i)12 = [(1+i)²]6 = (2i)6 = 64i6 = −64.
(iv) If 5 is the harmonic mean between 2 and b, find b.
H = 2ab/(a+b): 5 = 4b/(2+b) ⇒ 10 + 5b = 4b ⇒ b = −10.
(v) Evaluate
9!6! 3!.
= (9·8·7)/(3·2·1) = 504/6 = 84.
(vi) How many signals can be given by 6 flags of different colours, using 2 flags at a time?
6P2 = 6 × 5 = 30.
(vii) How many diagonals and triangles can be formed by joining the vertices of a polygon having 15 sides?
Diagonals = n(n−3)/2 = 15×12/2 = 90. Triangles = 15C3 = 15·14·13/6 = 455.
(viii) When 4x&sup4; + 2x³ + kx² + 13 is divided by x + 1, the remainder is 16. Find k.
f(−1) = 4 − 2 + k + 13 = 16 ⇒ k = 1.
(ix) For P(x) = 3x³ − 4x² + 2x − 5, predict the value at x = −1.
P(−1) = −3 − 4 − 2 − 5 = −14.
(x) Prove: sin 210° + cos 240° + tan 225° + cot 225° = 1.
sin210° = −½, cos240° = −½, tan225° = 1, cot225° = 1. Sum = −1 + 2 = 1. ✓
(xi) Prove: cos(α + 45°) =
1√2(cosα − sinα).
cosαcos45° − sinαsin45° = (1/√2)cosα − (1/√2)sinα = (1/√2)(cosα − sinα). ✓
(xii) Express sin 5x + sin 7x as a product.
sinP + sinQ = 2 sin[(P+Q)/2] cos[(P−Q)/2] = 2 sin 6x cos x.
4. Write short answers to any NINE (09) questions:2 × 9 = 18
(i) Find the period of
12 sin(
3x2 −
π2).
Period = 2π/(3/2) = 4π/3.
(ii) Find the maximum and minimum values of
32 + cos(x −
π4).
−1 ≤ cos(·) ≤ 1 ⇒ Max = 3/2 + 1 = 5/2, Min = 3/2 − 1 = 1/2.
(iii) Evaluate lim
x→3 (x − 3)/(√x − √3).
x − 3 = (√x − √3)(√x + √3), so limit = lim (√x + √3) = 2√3.
(iv) Evaluate lim
n→+∞ (1 + 4/n)
n.
Using lim(1 + a/n)n = ea: e&sup4;.
(v) Define divergent sequence.
A sequence which is not convergent (has no finite limit) is called divergent, e.g. 1, 2, 3, 4, …
(vi) s(t) = 4t² + 2t + 1 (miles). Find the average velocity over [2, 5].
s(2) = 21, s(5) = 111. Avg velocity = (111 − 21)/(5 − 2) = 90/3 = 30 miles/hour.
(vii) Find the gradient of f(x) = 3x² + 2x at x = 1.
f′(x) = 6x + 2; f′(1) = 8.
(viii) Find dy/dx if y =
34x&sup4; +
23x³ +
12x² + 2x + 5.
dy/dx = 3x³ + 2x² + x + 2.
(ix) Differentiate (2x − 3)/(2x + 1) w.r.t. x.
= [(2x+1)(2) − (2x−3)(2)]/(2x+1)² = (4x+2−4x+6)/(2x+1)² = 8/(2x+1)².
(x) If u = 2i+3j+k, v = 4i+6j+2k, w = −6i−9j−3k, show that u, v, w are parallel.
v = 2u and w = −3u, so all are scalar multiples of u ⇒ parallel.
(xi) Find t so that |2i + (t−1)j + tk| = √13.
4 + (t−1)² + t² = 13 ⇒ 2t² − 2t − 8 = 0 ⇒ t² − t − 4 = 0 ⇒ t = (1 ± √17)/2.
(xii) Work done by F = 2i + 5j + 3k moving from P
1(2, −3, 1) to P
2(7, 5, 3).
d = (5, 8, 2). W = F·d = 10 + 40 + 6 = 56 units.
(xiii) Show that |a×b|² = |a|²|b|² − (a·b)².
|a×b|² = |a|²|b|²sin²θ = |a|²|b|²(1 − cos²θ) = |a|²|b|² − (|a||b|cosθ)² = |a|²|b|² − (a·b)². ✓
Subjective (Part-II)
Note: Attempt any three questions.3 × 10 = 30
5. (a) If z
1 = x + yi, z
2 = a + bi, find x, y, a, b such that z
1 + z
2 = 10 + 4i and z
1 − z
2 = 6 + 2i. (5)
Step 1: (x+a) + (y+b)i = 10 + 4i ⇒ x + a = 10, y + b = 4.
Step 2: (x−a) + (y−b)i = 6 + 2i ⇒ x − a = 6, y − b = 2.
Step 3: Add: 2x = 16 ⇒ x = 8; so a = 2. Add: 2y = 6 ⇒ y = 3; so b = 1.
Ans: x = 8, y = 3, a = 2, b = 1.
(b) Solve |x² − 3x + 2| > 4. (5)
Step 1: |A| > 4 ⇒ A > 4 or A < −4.
Step 2: x² − 3x + 2 > 4 ⇒ x² − 3x − 2 > 0; roots (3 ± √17)/2 ⇒ x < (3−√17)/2 or x > (3+√17)/2.
Step 3: x² − 3x + 2 < −4 ⇒ x² − 3x + 6 < 0; discriminant 9 − 24 < 0 ⇒ no real solution.
Solution set: (−∞, (3−√17)/2) ∪ ((3+√17)/2, ∞).
6. (a) Show that det[ a−b−c, 2a, 2a ; 2b, b−c−a, 2b ; 2c, 2c, c−a−b ] = (a+b+c)³. (5)
Step 1: R1 → R1+R2+R3: every entry of row 1 becomes (a+b+c). Take it common: (a+b+c)·|1 1 1; 2b b−c−a 2b; 2c 2c c−a−b|.
Step 2: C2 → C2−C1, C3 → C3−C1: row 1 = (1, 0, 0); row 2 = (2b, −(a+b+c), 0); row 3 = (2c, 0, −(a+b+c)).
Step 3: Expand along R1: 1·[(a+b+c)(a+b+c)] = (a+b+c)².
Step 4: Result = (a+b+c)(a+b+c)² = (a+b+c)³. ✓
(b) Resolve (x² − 10x + 13)/[(x−1)(x² − 5x + 6)] into partial fractions. (5)
Step 1: x²−5x+6 = (x−2)(x−3). Let = A/(x−1) + B/(x−2) + C/(x−3).
Step 2: x²−10x+13 = A(x−2)(x−3) + B(x−1)(x−3) + C(x−1)(x−2).
Step 3: x=1: 4 = 2A ⇒ A = 2. x=2: −3 = −B ⇒ B = 3. x=3: −8 = 2C ⇒ C = −4.
Ans: 2/(x−1) + 3/(x−2) − 4/(x−3).
7. (a) For what value of n is (a
n + b
n)/(a
n−1 + b
n−1) the positive G.M. between a and b? (5)
Step 1: Set equal to √(ab): an + bn = an−½b½ + a½bn−½.
Step 2: an − an−½b½ = a½bn−½ − bn ⇒ an−½(a½ − b½) = bn−½(a½ − b½).
Step 3: Cancel (a½−b½) ⇒ an−½ = bn−½ ⇒ n − ½ = 0. n = ½.
(b) How many numbers between 100 and 1000 can be formed using digits 0,1,2,3,4,5 without repetition? How many are divisible by 5? (5)
Step 1 (all): Hundreds: 5 ways (not 0); tens: 5; units: 4 ⇒ 5×5×4 = 100.
Step 2 (ends in 0): 5 × 4 = 20.
Step 3 (ends in 5): hundreds 4 ways (not 0, 5), tens 4 ways ⇒ 16.
Divisible by 5: 20 + 16 = 36.
8. (a) Prove that sin(π/9) sin(2π/9) sin(π/3) sin(4π/9) = 3/16. (5)
Step 1: In degrees: sin20° sin40° sin60° sin80°.
Step 2: Identity sinθ sin(60°−θ) sin(60°+θ) = ¼ sin3θ. With θ = 20°: sin20° sin40° sin80° = ¼ sin60° = √3/8.
Step 3: Multiply by sin60° = √3/2: (√3/8)(√3/2) = 3/16. ✓
(b) f(x) = 2x + 3 for x ≤ 1; −x + 4 for x > 1. Discuss limit and continuity at x = 1. (5)
Step 1: LHL = lim(2x+3) = 5. Step 2: RHL = lim(−x+4) = 3. Step 3: f(1) = 5.
LHL ≠ RHL ⇒ limit does not exist, hence f is discontinuous at x = 1.
9. (a) Differentiate (√x + 1)(x
3/2 − 1)/(x
3/2 − x
1/2) w.r.t. x. (5)
Step 1: Denominator = √x(x − 1). Numerator: x3/2 − 1 = (√x − 1)(x + √x + 1), so (√x+1)(√x−1)(x+√x+1) = (x−1)(x+√x+1).
Step 2: y = (x + √x + 1)/√x = √x + 1 + x−1/2.
Step 3: dy/dx = 1/(2√x) − 1/(2x3/2).
(b) If |a| = 3, |b| = 4 and |a + b| = 5, find the angle between a and b. (5)
Step 1: |a+b|² = |a|² + |b|² + 2a·b ⇒ 25 = 9 + 16 + 2a·b ⇒ a·b = 0.
Step 2: cosθ = 0 ⇒ θ = 90°.