WAEC Mathematics Past Questions & Answers - Page 183

911.

A bag contains 3 red and 2 white identical balls. lf 2 balls are picked at random from the bag, one after the other and with replacement, find the probability that they are of different colours

A.

\(\frac{36}{625}\)

B.

\(\frac{16}{625}\)

C.

\(\frac{12}{25}\)

D.

\(\frac{13}{25}\)

Correct answer is C

Prob(RW or WR) = Prob(RW) + Prob(WR)
\(Prob(R) = \frac{3}{5}:Prob(W) = \frac{2}{5}\\
Prob(RW\hspace{1mm}or\hspace{1mm}WR)=\frac{3}{5}\times\frac{2}{5}+\frac{2}{5}\times \frac{3}{5}\\
\frac{6}{25}+\frac{6}{25}=\frac{12}{25}\)

912.

A Cooperative Society, charges an interest of 51/2% per annum on any amount borrowed by its members. If a member borrows N125,000, how much does he pay back after one year?

A.

N136875

B.

N131,875

C.

N126750

D.

N126250

Correct answer is B

The rate of interest charge = 51/2% p.a
The amount borrowed = N125, 000:00
Interest charge \(=\frac{11}{200} of N125,000\\
= 11 \times N625.00 = N6,875.00\)
The amount refunded by the member with interest charge by the cooperative society
N125,000+N6,875.00 = N131,875.00

913.

Given that p = 2, q = -5 and r = - 4, evaluate 3p2 - q2 - r3

A.

101

B.

77

C.

51

D.

-27

Correct answer is C

3(2)2 - (-5)2 - (-4)3
3(4) – (25) – (-64); 12 – 25 + 64 = 51

914.

The sides of two cubes are in the ratio 2:5. What is the ratio of their volumes?

A.

4:5

B.

8:15

C.

6:125

D.

8:125

Correct answer is D

The ratio of the two cubes = 2:5
Volume of the two cubes = 2\(^3\) : 5\(^3\) = 8 : 125