WAEC Mathematics Past Questions & Answers - Page 69

341.

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

342.

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

343.

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;

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

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

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

344.

The figure is a pie chart which represents the expenditure of a family in a year. If the total income of the family was Le 10,800,000.00, how much was spent on food?

A.

Le 2,250,000.00

B.

Le 22,700,000.00

C.

Le 3,600,000.00

D.

Le 4,500,000.00

Correct answer is C

sectoral angle representing food

= 360o - (80 + 70 + 90)o

= 120o

Amount spent on food

= \(\frac{\tect{sectoral angle}}{360^o}\) x Le 10,800,000

= Le 3,600,000

345.

In the diagram, TX is perpendicular to UW, |UX| = 1cm and |TX| = |WX| = \(\sqrt{3}\)cm. Find UTW

A.

135o

B.

105o

C.

75o

D.

60o

Correct answer is C

In \(\Delta\) UXT, tan\(\alpha\) = \(\frac{1}{\sqrt{3}}\)

\(\alpha\) = tan-1(\(\frac{1}{\sqrt{3}}\))

= 30o

In \(\Delta\)WXT, tan\(\beta\) \(\frac{\sqrt{3}}{\sqrt{3}}\) = 1

\(\beta\) = tan-1(1) = 45o

Hence, < UTW = \(\alpha\) + \(\beta\)

= 30o + 45o = 75o