WAEC Mathematics Past Questions & Answers - Page 220

1,096.

Express 0.0462 in standard form

A.

0.460 x 10-1

B.

0.462 x 10-2

C.

4.62 x 10-1

D.

4.62 x 10-2

Correct answer is D

No explanation has been provided for this answer.

1,097.

If N varies directly as M and N = 8 when M = 20 find M when N = 7

A.

13

B.

15

C.

\(17\frac{1}{2}\)

D.

\(18\frac{1}{2}\)

Correct answer is C

N ∝ M
∴N = kM where k is a constant
N = 8 when M = 20
∴ 8 = k x 20
\(k = \frac{8}{20} = \frac{2}{5}\\
∴ N = \frac{2}{5}M\\
If N = 7\\
∴ 7 = \frac{2}{5}M\\
M = \frac{35}{2} = 17\frac{1}{2}\)

1,098.

In a class of 80 students, every students studies Economics or Geography or both. If 65 students study Economics and 50 study Geography, how many study both subjects?

A.

15

B.

30

C.

35

D.

45

Correct answer is C

Let c = no of students that offered both subjects ∴ No of students offering Economics = 65 - c No of students offering Geography = 50 - c 65 - c + c + 50 - c = 80 115 - c = 80 c = 35 35 students offer both Economics and Geography.

1,099.

Evaluate \(log_{10}5 + log_{10}20\)

A.

2

B.

3

C.

4

D.

5

Correct answer is A

\(log_{10}5 + log_{10}20\\
log_{10}[5\times 20]\\
log_{10}100\\
log_{10}10^2\\
2log_{10}10=2\)

1,100.

Evaluate \((20_{three})^2 - (11_{three})^2\) in base three

A.

101

B.

121

C.

202

D.

2020

Correct answer is C

\((20_{three})^2 - (11_{three})^2\)

= \((20_{3} - 11_{3})(20_{3} + 11_{3})\)

= \((2_{3})(101_{3})\)

= \(202_{3}\)