Question

There is a bag with only red marbles and blue marbles.
The probability of randomly choosing a blue marble is
7
12
.
There are 84 marbles in total in the bag and each is equally likely to be chosen.
Work out how many red marbles there must be.

Answer 1

Answer:

The probability of randomly choosing a red marble is 5/8. There are 72 marbles in total in the bag and each is equally likely to be chosen.

Answer 2

Step-by-step explanation:

If the marble is not "replaced", the probability of the second drawing changes, since there are less marbles in the jar. The probability of drawing a red marble = 2/5. The probability of drawing a blue marble is now = 1/4. The probability of drawing a red marble = 2/5.