WAEC Mathematics Past Questions & Answers - Page 109

541.

The sum of the interior angles of regular polygon is 1800o. How many sides has the polygon?

A.

16

B.

12

C.

10

D.

8

Correct answer is B

Sum = (n - 2)180

1800 = (n - 2)180

divide both sides by 180o

\(\frac{1800}{180}\) = (n - 2)\(\frac{180}{180}\)

10 = n - 2

10 + 2 = n

n = 12

542.

Solve (\(\frac{27}{125}\))-\(\frac{1}{3}\) x (\(\frac{4}{9}\))\(\frac{1}{2}\)

A.

\(\frac{10}{9}\)

B.

\(\frac{9}{10}\)

C.

\(\frac{2}{5}\)

D.

\(\frac{12}{125}\)

Correct answer is A

(\(\frac{27}{125}\))-\(\frac{1}{3}\) x (\(\frac{4}{9}\))\(\frac{1}{2}\)

= (\(\frac{3^3}{5^3}\))-\(\frac{1}{3}\)-\(\frac{1}{3}\) x (\(\frac{3^2}{3^2}\))\(\frac{1}{2}\) -\(\frac{1}{2}\)

= \(\frac{3^{-1}}{3^{-1}} \times \frac{2}{3}\)

= \(\frac{\frac{1}{3}}{\frac{1}{5}} \times \frac{2}{3}\)

\(\frac{1}{3} \times \frac{5}{1} \times {2}{3} = \frac{10}{9}\)

543.

Alfred spent \(\frac{1}{4}\) of his money on food, \(\frac{1}{3}\) on clothing and save the rest. If he saved N72,20.00, how much did he spend on food?

A.

N43,200.00

B.

N43,000.00

C.

N42,200.00

D.

N40,000.00

Correct answer is A

let the total amount be Nx i.e (\(\frac{1}{4}\))x + (\(\frac{1}{3}\))x + 72,000 = x

\(\frac{x}{4} + \frac{x}{4} + 72,000 = x\)

\(\frac{3x + 4x + 86,400}{12} = x\)

cross multiply to clear fraction

12x = 3x + 4x + 86,400

12x - 7x = 86,400

5x = 86,400

x - \(\frac{86,400}{5}\) = 172,800

amount spent on food = \(\frac{1}{4} \times 172,800\)

= N43,200

544.

If p = {prime factors of 210} and Q = {prime less than 10}, find p \(\cap\) Q

A.

{1,2, 3}

B.

{2, 3, 5}

C.

{1, 3, 5,7}

D.

{2,3,5,7}

Correct answer is D

prime factor of 210 = 2, 3, 5, 7

prime numbers less than 10 = 2, 3, 5 , 7

545.

Express 3 - [\(\frac{x - y}{y}\)] as a single fraction

A.

\(\frac{3xy}{y}\)

B.

\(\frac{x - 4y}{y}\)

C.

\(\frac{4y - x}{y}\)

D.

3 - \(\frac{x - y}{y}\)

Correct answer is C

(\(\frac{x -y}{y}\)); \(\frac{3}{1} - \frac{x y}{y}\)

= \(\frac{3y - (x - y)}{y}\)

= \(\frac{3y - x + y}{y}\)

= \(\frac{4y - x}{y}\)