Question

A bag contains 15 blue marbles, 5 red marbles, and 11 green marbles. How many blue marbles must be removed

from the 31 marbles in the bag so that the probability of randomly drawing a blue marble is 1/3


07
O 12
06
09
O 11

Answer 1

7

Explanation:

It is 7:

31 - 7 = 24

15 - 7 = 8

8/24 = 1/3 = 33%

It is not 12:

31 - 12 = 19

15 - 12 = 3

3/19 = 15%

It is not 6:

31 - 6 = 25

15 - 6 = 9

9/25 = 36%

It is not 9:

31 - 9 = 22

15 - 9 = 7

7/22 = 31%

It is not 11:

31 - 11 = 20

15 - 11 = 4

4/20 = 20%

I subtracted the option from 31 (the new total of marbles) and from 15 (the new total of blue marbles). Then, I divided the new total by the new total of the blue marbles. I converted the decimal into a percentage. If the percentage was not 33%, then it was not the answer.