Mathematics 2004 JAMB Past Questions - Question 48: Some white balls were put in a basket containing twelve red balls and sixteen black balls.If the probability of picking a white ball from the basket is 3/7, how many white balls were introduced?

Correct Answer

C

Explanation

Let's assume the number of white balls introduced is 'x'.The total number of balls in the basket before introducing the white balls is 12 + 16 = 28.After introducing 'x' white balls, the total number of balls in the basket becomes 28 + x.The probability of picking a white ball from the basket is given as 3/7.The probability of picking a white ball can be calculated as the ratio of the number of white balls to the total number of balls in the basket:x / (28 + x) = 3/7To solve this equation, we can cross-multiply:7x = 3(28 + x)7x = 84 + 3xSubtracting 3x from both sides:4x = 84Dividing both sides by 4:x = 21Therefore, 21 white balls were introduced into the basket.