JAMB Mathematics Past Questions & Answers - Page 31

151.

Each of the interior angles of a regular polygon is 140°. How many sides has the polygon?

A.

9

B.

9

C.

7

D.

5

Correct answer is A

Each interior angle = \(\frac{(n - 2)180}{n}\)

140 = \(\frac{(n - 2)180}{n}\)

Cross multiply:

140n = 180n - 360

40n = 360

n = 9 sides ( A Nonagon)

152.

Find the length of a side of a rhombus whose diagonals are 6cm and 8cm

A.

8cm

B.

5cm

C.

4cm

D.

3cm

Correct answer is B

The diagonal of a rhombus is a line segment that joins any two non-adjacent vertices.

A rhombus has two diagonals that bisect each other at right angles.

i.e this splits 6cm into 3cm each AND 8cm to 4cm

Using Hyp\(^2\) = adj\(^2\) + opp\(^2\)

Hyp\(^2\) = 3\(^2\) + 4\(^2\)

Hyp\(^2\) = 25

Hyp = 5

∴ Length (L) is 5cm because a rhombus is a quadrilateral with 4 equal lengths

153.

The angle of a sector of a circle, radius 10.5cm, is 48°, Calculate the perimeter of the sector

A.

8.8cm

B.

25.4cm

C.

25.6cm

D.

29.8cm

Correct answer is D

Length of Arc AB = \(\frac{\theta}{360}\) 2\(\pi\)r

= \(\frac{48}{360}\) x 2\(\frac{22}{7}\) x \(\frac{21}{2}\)

= \(\frac{4 \times 22 \times \times 3}{30}\) \(\frac{88}{10}\) = 8.8cm

Perimeter = 8.8 + 2r

= 8.8 + 2(10.5)

= 8.8 + 21

= 29.8cm

154.

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

Correct answer is A

PQ\(^2\) = (x2 - x1)\(^2\)  + (y2 - y1)\(^2\) 

= 12\(^2\)  + 5\(^2\) 
= 144 + 25
= 169

PQ = √169 = 13

But PQ = diameter = 2r, r = PQ/2 = 6.5 units

155.

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

Correct answer is B

use "T" to represent the total profit. The first receives \(\frac{1}{3}\) T

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

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

The seconds receives the remaining, which is \(\frac{2}{3}\) also

\(\frac{2}{3}\) x \(\frac{2}{3}\) x \(\frac{4}{9}\)

The third receives the left over, which is \(\frac{2}{3}\)T - \(\frac{4}{9}\)T = (\(\frac{6 - 4}{9}\))T

= \(\frac{2}{9}\)T

The third receives \(\frac{2}{9}\)T which is equivalent to N12000

If \(\frac{2}{9}\)T = N12, 000

T = \(\frac{12 000}{\frac{2}{9}}\)

= N54, 000