WAEC Mathematics Past Questions & Answers - Page 215

1,071.

If the probability that an event will occur is p and the probability that it will not occur is q, which of the following is true?

A.

p-q=1

B.

q-p=0

C.

p+q=1

D.

p+q=0

Correct answer is C

No explanation has been provided for this answer.

1,072.

A box contains 5 red, 3 green and 4 blue balls. A boy is allowed to take away two balls from the box. What is the probability that one is green and the other is blue?

A.

\(\frac{2}{11}\)

B.

\(\frac{5}{12}\)

C.

\(\frac{8}{12}\)

D.

\(\frac{7}{11}\)

Correct answer is A

Total number of balls = 5 + 3 + 4 = 12 balls

P(one ball is green and the other is blue) = P(first ball is green and second blue) + P(first ball is blue and the second green)

 = \(\frac{3}{12} \times \frac{4}{11} + \frac{4}{12} \times \frac{3}{11}\)

= \(\frac{2}{11}\)

1,073.

A box contains 5 red, 3 green and 4 blue balls. A boy is allowed to take away two balls from the box. What is the probability that the two balls are red?

A.

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

B.

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

C.

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

D.

\(\frac{31}{36}\)

Correct answer is A

Total number of balls = 5 + 3 + 4 

= 12 balls

P(first ball is red) = \(\frac{5}{12}\)

P(second ball is red) = \(\frac{4}{11}\)

\(\therefore\) P(both balls are red) = \(\frac{5}{12} \times \frac{4}{11}\)

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

1,074.

Express 25° 45' in decimal (Hint: 1° = 60')

A.

25.75o

B.

25.55o

C.

25.45o

D.

25.15o

Correct answer is A

25° 45' = 25° + \(\frac{45}{60}\)°

= 25° + 0.75°

= 25.75°

1,075.

Three observation posts P,Q and R are such that Q is due east of P and R is due north of Q. If |PQ| = 5km and |PR| = 10km, find |QR|

A.

5.0km

B.

7.5km

C.

7.6km

D.

8.7km

Correct answer is D

\((PR)^2 = (PQ)^2 + (QR)^2\)

\(10^2 = 5^2 + (QR)^2\)

\((QR)^2 = 100 - 25\)

\(QR = \sqrt{75}\)

= \(8.660\)

\(\approxeq\) 8.7 km