Question

A bag contains only blue balls and green balls. There are $6$ blue balls. If the probability of drawing a blue ball at random from this bag is $\dfrac14,$ then the number of green balls in the bag is

$12$

$18$

$24$

$30$

$36$

Answer: B

Concepts:basic probability ratio and proportion

Difficulty rating: 860

Solution:

Since blue balls make up $\dfrac14$ of the bag and there are $6$ of them, the total is $6 \cdot 4 = 24$ balls.

So the number of green balls is $24 - 6 = 18$ .

Thus, the correct answer is B .

1990 AMC 8 Problem 14

Answer: B

Difficulty rating: 860

Solution:

Problem 14 in Other Years