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?

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

542.

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

543.

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

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

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

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

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

544.

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

A.

1\(\frac{1}{4}\)

B.

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

C.

3\(\frac{3}{4}\)

D.

5

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?

A.

log y = log 8 x log \(\sqrt{m}\)

B.

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

C.

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

D.

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

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