WAEC Mathematics Past Questions & Answers - Page 30

146.

A box contains 12 identical balls of which 5 are red, 4 blue, and the rest are green. If two balls are selected at random one after the other with replacement, what is the probability that both are red? 

A.

\(\frac{25}{144}\)

B.

\(\frac{5}{33}\)

C.

\(\frac{5}{6}\)

D.

\(\frac{103}{132}\)

Correct answer is A

Pr(RR) = \(\frac{5}{12}\) = \(\frac{5}{12} \times \frac{5}{12} = \frac{25}{144}\)

147.

A box contains 12 identical balls of which 5 are red, 4 blue, and the rest are green.  If a ball is selected at random from the box, what is the probability that it is green? 

A.

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

B.

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

C.

\(\frac{1}{3}\)

D.

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

Correct answer is D

No. of red = 5

No. of blue = 4

No. of green = 3

Total = 12

Pr(Green) = \(\frac{3}{12} = \frac{1}{4}\)

148.

Find the sum of the interior angle of a pentagon.

A.

340\(^o\)

B.

350\(^o\)

C.

540\(^o\)

D.

550\(^o\)

Correct answer is C

Sum = (5 - ) 180\(^o\) 

= (5 - 2) 180\(^o\)  = 3 x 180\(^o\)  

= 540\(^o\)

149.

The mean of the numbers 15, 21, 17, 26, 18, and 29 is 21. Calculate the standard deviation 

A.

9

B.

6

C.

5

D.

0

Correct answer is C

x

x - \(\overline{x}\))\(^2\) (x - \(\overline{x}\))\(^2\)

15

21

17

26

18

29

-6

0

-4

5

-3

-8

36

0

16

25

9

64

    \(\sum (x - \overline{x})^2\) = 150

 

Standard deviation = \(\sqrt{\frac{ \sum (x - \overline{x})^2}{n} }\)

= \(\frac{150}{6}\)

= \(\sqrt{25}\)

= 5

150.

The pie chart shows the population of men, women, and children in a city. If the population of the city is 1,800,000, how many men are in the city?

A.

845,000

B.

600,000

C.

355,000

D.

250,000

Correct answer is C

Angle of Men = 360\(^o\) - (120 + 169) 

= 360\(^o\) - 289\(^o\) = 71\(^o\)

No. of men \(\frac{71}{360}\) x 1800,000

= 355,000