Question

5. Three red balls, five green balls and a number of blue balls are put together in a sack. One ball is picked at random from the sack. If the probability of picking a red ball is 1/6, find:
(a) the number of blue balls in the sack;
(b) the probability of picking a green ball.

Accepted Answer

Red = 3, Green = 5, Blue = x (unknown), total balls = 3+5+x = 8+x.
(a) P(red) = 3/(8+x) = 1/6 ⇒ cross-multiplying: 3×6 = 8+x ⇒ 18 = 8+x ⇒ x = 10. So there are 10 blue balls.
(b) Total balls = 8+10 = 18. P(green) = 5/18 ≈ 0.2778.

WAEC Mathematics 2019 Theory — Question 6

Sign up free to unlock