JAMB Mathematics Past Questions 2021

10 questions from the JAMB 2021 Mathematics paper, with answers and explanations. Tap "Show answer" under each one when you are ready.

JAMB 2021Question 1 · Algebraic Processes

Solve the following equation:

\frac{2}{( 2 r - 1 )}

\frac{5}{3}

\frac{1}{( r + 2 )}

A.( -1, $\frac{5}{2}$ )
B.( 1, - $\frac{5}{2}$ )
C.( $\frac{5}{2}$ , 1 )
D.(2,1)

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Answer: B. ( 1, - $\frac{5}{2}$ )

Clearing fractions gives 2r²+3r-5=0, so r=1 or -5/2.

JAMB 2021Question 2 · Algebraic Processes

Factorize completely

81 a^{4}

16 b^{4}

A.(3a + 2b)(2a - 3b)(9a 2 + 4b 2 )
B.(3a - 2b)(2a - 3b)(4a 2 - 9b 2 )
C.(3a - 2b)(3a + 2b)(9a 2 + 4b 2 )
D.(6a - 2b)(8a - 3b)(4a 3 - 9b 2 )

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Answer: C. (3a - 2b)(3a + 2b)(9a 2 + 4b 2 )

81a⁴-16b⁴=(9a²-4b²)(9a²+4b²)=(3a-2b)(3a+2b)(9a²+4b²).

JAMB 2021Question 3 · Calculus

Find the derivative of the function y =

2 x^{2}

(2x - 1) at the point x = -1?

A.18
B.16
C.-4
D.-6

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Answer: B. 16

y=4x³-2x²; dy/dx=12x²-4x; at x=-1 this is 16.

JAMB 2021Question 4 · Coordinate Geometry and Trigonometry

P(-6, 1) and Q(6, 6) are the two ends of the diameter of a given circle. Calculate the radius.

A.6.5 units
B.13.0 units
C.3.5 units
D.7.0 units

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Answer: A. 6.5 units

Diameter= $1 2^{2} + 5^{2}$ =13; radius=6.5.

JAMB 2021Question 5 · Geometry and Mensuration

The angle of a sector of a circle, radius

10.5 cm

, is

4 8^{\circ}

, Calculate the perimeter of the sector

A. $8.8 cm$
B. $25.4 cm$
C. $25.6 cm$
D. $29.8 cm$

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Answer: D. $29.8 cm$

Arc≈ $8.8 cm$ ; perimeter=8.8+21= $29.8 cm$ .

JAMB 2021Question 6 · Geometry and Mensuration

The locus of a point which moves so that it is equidistant from two intersecting straight lines is the?

A.perpendicular bisector of the two lines
B.angle bisector of the two lines
C.bisector of the two lines
D.line parallel to the two lines

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Answer: B. angle bisector of the two lines

Locus equidistant from two intersecting lines is their angle bisector.

JAMB 2021Question 7 · Number, Fractions, and Approximation

Correct 241.34

(3 \times 1 0^{- 3})^{2}

to 4 significant figures

A.0.0014
B.0.001448
C.0.0022
D.0.002172

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Answer: D. 0.002172

241.34×(0.003)²=0.00217206≈0.002172.

JAMB 2021Question 8 · Number, Fractions, and Approximation

Three brothers in a business deal share the profit at the end of a contract. The first received

\frac{1}{3}

of the profit and the second

\frac{2}{3}

of the remainder. If the third received the remaining N12000.00 how much profit did they share?

A.N60 000.00
B.N54 000.00
C.N48 000.00
D.N42 000.00

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Answer: B. N54 000.00

Third share= $\frac{2}{9}$ of profit=12,000, so total=54,000.

JAMB 2021Question 9 · Sequences, Series, and Variation

What is the n-th term of the sequence 2, 6, 12, 20...?

A.4n - 2
B.2(3 n - 1 )
C. $n^{2} + n$
D. $n^{2} + 3 n + 2$

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Answer: C. $n^{2} + n$

Sequence matches n²+n.

JAMB 2021Question 10 · Statistics and Probability

4, 16, 30, 20, 10, 14 and 26 are represented on a pie chart. Find the sum of the angles of the bisectors representing all numbers equals to or greater than 16

A. $4 8^{\circ}$
B. $8 4^{\circ}$
C. $9 2^{\circ}$
D. $27 6^{\circ}$

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Answer: D. $27 6^{\circ}$

Values ≥16 sum to 92 of total 120; angle=92×3= $27 6^{\circ}$ .

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