JAMB Mathematics Past Questions & Answers - Page 266

1,326.

The three sides of an isosceles triangle are length of lengths (x + 3), (2x + 3), (2x - 3) respectively. Calculate x.

A.

5

B.

1

C.

6

D.

3

Correct answer is D

2x + 3 \(\neq\) 2x - 3 for any value of x

∴ for the \(\bigtriangleup\) to be isosceles, either

2x - 3 = x + 3 or 2x + 3 = x + 3

solve the two equations we arrive at

x = 6 or x = 0

When x = 6, the sides are 9, 15, 9

When x = 0, the sides are 3, 4, -3 since lengths of a \(\bigtriangleup\)can never be negative then the value of x = 6

1,327.

Calculate the length in cm. of the area of a circle of diameter 8cm which subtends an angle of 22\(\frac{1}{2}\)o at the centre of the circle

A.

2\(\pi\)

B.

\(\pi\)

C.

\(\frac{2}{3}\)

D.

\(\frac{\pi}{2}\)

Correct answer is D

Diameter = 8cm

∴ Radius = 4cm

Length of arc = \(\frac{\theta}{360}\) x 2 \(\pi\)r but Q = 22\(\frac{1}{2}\)

∴ Length \(\frac{22\frac{1}{2}}{360}\) x 2 x \(\pi\) x 4

= \(\frac{22\frac{1}{2} \times 8\pi}{360}\)

= \(\frac{180}{360}\)

= \(\frac{\pi}{2}\)

1,328.

A rectangular polygon has 150o as the size of each interior angle. How many sides has the polygon?

A.

12

B.

10

C.

9

D.

8

Correct answer is A

A rectangular polygon has each interior angle to be 150o

let the polygon has n-sides

therefore, Total interior angle 150 x n = 150n

hence 150n = (2n - 4)90

150n = 180n - 360

360 = (180 - 150)n

30n = 360

n = 12

1,329.

A man's initial salary is N540.00 a month and increases after each period of six months by N36.00 a month. Find his salary in the eighth month of the third year

A.

N828.00

B.

N756.00

C.

N720.00

D.

N684.00

Correct answer is C

Initial salary = N540 increment = N36 (every 6 months) Period of increment = 2 yrs and 6 months amount(increment) = N36 x 5 = N180 The man's new salary = N540 = N180 = N720.00

1,330.

If k + 1; 2k - 1, 3k + 1 are three consecutive terms of a geometric progression, find the possible values of the common ratio

A.

0, 8

B.

-1, \(\frac{5}{3}\)

C.

2, 3

D.

1, -1

Correct answer is B

\(\frac{2k - 1}{k + 1} = \frac{3k + 1}{2k - 1}\)

\((k + 1)(3k + 1) = (2k - 1)(2k - 1)\)

\(3k^{2} + 4k + 1 = 4k^{2} - 4k + 1\)

\(4k^{2} - 3k^{2} - 4k - 4k + 1 - 1 = 0\)

\(k^{2} - 8k = 0\)

\(k(k - 8) = 0\)

\(\therefore \text{k = 0 or 8}\)

The terms of the sequence given k = 0: (1, -1, 1)

\(\implies \text{The common ratio r = -1}\)

The terms of the sequence given k = 8: (9, 15, 25)

\(\implies \text{The common ratio r = } \frac{5}{3}\)

The possible values of the common ratio are -1 and \(\frac{5}{3}\).