WAEC Mathematics Past Questions & Answers - Page 69

341.

Express 1975 correct to 2 significant figures

A.

20

B.

1,900

C.

1,980

D.

2,000

Correct answer is D

No explanation has been provided for this answer.

342.

A sphere of radius rcm has the same volume as cylinder of radius 3cm and height 4cm. Find the value of r

A.

\(\frac{2}{3}\)

B.

2

C.

3

D.

6

Correct answer is C

Volume of sphere = Volume of cylinder

i.e. \(\frac{4}{3} \pi r^3 = \pi r^2 h\)

\(\frac{4}{3} \pi r^3 = \pi \times 3^2 \times 4\)

r3 = \(\frac{\pi \times 9 \times 4 \times 3}{4 \pi}\)

r = 3\(\sqrt{27}\)

= 3

343.

If log2(3x - 1) = 5, find x.

A.

2.00

B.

3.67

C.

8.67

D.

11

Correct answer is D

Log2(3x - 1) = 5

Log2(3x - 1) = Log225

Log2(3x - 1) = Log232

3x - 1 = 32

3x = 32 + 1 = 33

x = \(\frac{33}{3}\)

= 11

344.

The marks of eight students in a test are: 3, 10, 4, 5, 14, 13, 16 and 7. Find the range

A.

16

B.

14

C.

13

D.

11

Correct answer is C

First, arrange the marks in order of magnitude; 3, 4, 5, 7, 10, 13, 14, 16

Hence range = 16 - 3 = 13

345.

A fair die is thrown two times. What is the probability that the sum of the scores is at least 10?

A.

\(\frac{5}{36}\)

B.

\(\frac{1}{6}\)

C.

\(\frac{5}{18}\)

D.

\(\frac{2}{3}\)

Correct answer is B

\(\begin{array}{c|c}
& 1 & 2 & 3 & 4 & 5 & 6 \\
\hline
1 & 1,1 & 1,2 & 1,3 & 1,4 & 1,5 & 1,6 \\ \hline 2 & 2,1 & 2,2 & 2,3 & 2,4 & 2,5 & 2,6 \\ \hline 3 & 3,1 & 3,2 & 3,3 & 3,4 & 3,5 & 3,6 \\ \hline 4 & 4,1 & 4,2 & 4,3 & 4,4 & 4,5 & 4,6 \\ 5 & 5,1 & 5,2 & 5,3 & 5,4 & 5,5 & 5,6 \\ \hline 6 & 6,1 & 6,2 & 6,3 & 6,4 & 6,5 & 6,6\end{array}\)

From the table above, event space, n(E) = 6

sample space, n(S) = 36

Hence, probability sum of scores is at least 10, is;

\(\frac{n(E)}{n(S)}\)

= \(\frac{6}{36}\)

= \(\frac{1}{6}\)