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WAEC Mathematics Past Questions & Answers - Page 109

541.

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?

N43,200.00

N43,000.00

N42,200.00

N40,000.00

View answer & explanation

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

542.

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

{1,2, 3}

{2, 3, 5}

{1, 3, 5,7}

{2,3,5,7}

View answer & explanation

Correct answer is D

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

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

543.

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

$\frac{3xy}{y}$

$\frac{x - 4y}{y}$

$\frac{4y - x}{y}$

3 - $\frac{x - y}{y}$

View answer & explanation

Correct answer is C

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

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

= $\frac{3y - x + y}{y}$

= $\frac{4y - x}{y}$

544.

If x + 0.4y = 3 and y = $\frac{1}{2}$ x, find the value of (x + y)

1 $\frac{1}{4}$

2 $\frac{1}{2}$

3 $\frac{3}{4}$

View answer & explanation

Correct answer is C

x + 0.4y = 3...(i)

y = $\frac{1}{2}$ x

x = 2y

x - 2y = 0....(ii)

solve simultaneously; x + 0.4y

= 3 - x - 2y = 0

2.4 = 3

y = $\frac{3 \times 10}{2.4 \times 10}$

= $\frac{30}{24} = \frac{5}{4}$

x - 2( $\frac{5}{4}$ ) = 0

x - $\frac{5}{2}$ = 0

x = $\frac{5}{2}$

x + y = $\frac{5}{2} + \frac{5}{4}$

$\frac{10 + 5}{4} = \frac{15}{4}$

= 3 $\frac{3}{4}$

545.

Which of these statements about y = 8 $\sqrt{m}$ is correct?

log y = log 8 x log $\sqrt{m}$

log y = 3 log 2 x $\frac{1}{2}$ log m

log y = 3 log 2 - $\frac{1}{2}$ log m

log y = 3 log 2 + $\frac{1}{2}$ log m

View answer & explanation

Correct answer is D

y = 8 $\sqrt{m}$ ; log y = log 8 $\sqrt{m}$

log y = log 8 + log $\sqrt{m}$

log y = log 2³ + log m^{$\frac{1}{2}$}

log y = 3 log 3 + $\frac{1}{2}$ log m