WAEC Mathematics Past Questions & Answers - Page 150

746.

P naira invested for 4 years invested for 4 years at r% simple interest per annum yields 0.36 p naira interest. Find the value of r

A.

1\(\frac{1}{9}\)

B.

1\(\frac{4}{9}\)

C.

9

D.

11

Correct answer is C

I = \(\frac{PRT}{100}\)

where r = r% p.a; I = 0.36p

0.36p = \(\frac{P \times r \times 4}{100}\)

\(\frac{0.36 \times 100}{4}\) = r

r = 9

747.

Simplify \(\sqrt{50} + \frac{10}{\sqrt{2}}\)

A.

10

B.

10\(\sqrt{2}\)

C.

20

D.

20\(\sqrt{2}\)

Correct answer is B

\(\sqrt{50} + \frac{10}}{\sqrt{2}} = \(\frac{\sqrt{50}}{1} + \sqrt{10}{\sqrt{2}}\)

= \(\frac{\sqrt{50 \times 2} + 10}{\sqrt{2}}\)

= \(\frac{\sqrt{100} + 10}{\sqrt{2}}\)

= \(\frac{10 + 10}{\sqrt{2} = \frac{20}{\sqrt{2}}\)

= \(\frac{20}{\sqrt{2}}\) \times \frac{\sqrt{2}}{\sqrt{2}}\)

= \(\frac{20\sqrt{2}}{2}\)

= 10\(\sqrt{2}\)

748.

Find the product of 0.0409 and 0.0021 leaving your answer in the standard form

A.

8.6 x 10-6

B.

8.6 x 105

C.

8.6 x 10-4

D.

8.6 x 10-5

Correct answer is D

0.0409 x 0.0021 = 409 x 10\(^{-4}\) x 21 x 10\(^{-4}\)

= 409 x 21 x 10\(^{-4 * -4}\)

= 8589 x 10\(^{-8}\)

= 8.589 x 10\(^{3}\) x 10\(^{-8}\)

= 8.6 x 10\(^{3-8}\)

= 8.6 x 10\(^{-5}\)

749.

Evaluate \(\frac{(3.2)^2 - (4.8)^2}{3.2 + 4.8}\)

A.

-0.08

B.

-1.60

C.

-10.24

D.

-12.80

Correct answer is B

\(\frac{(3.2)^2 - (4.8)^2}{3.2 + 1.8} = \frac{(3.2 - 4.8)(3.2 + 4.8)}{(3.2 + 4.8)}\)

= 3.2 - 4.8

= -1.60

750.

If x% of 240 equals 12, find x

A.

x = 1

B.

x = 3

C.

x = 5

D.

x = 7

Correct answer is C

x% of 240 = 12

\(\frac{x}{100} \times 240 = 12\)

x = \(\frac{12 \times 100}{240}\)

x = 5