Question

There is a bag with only red marbles and blue marbles.

The probability of randomly choosing a red 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

The probability of choosing a red marble is given as 7/12. This probability is the ratio of the number of red marbles to the total number of marbles.

Let's denote the number of red marbles as
`\( R \)`.

So, we have the equation:

`\( R / 84 = 7 / 12 \)`

We can solve this equation to find the value of
`\( R \)`.

The solution to the equation is
`\( R = 49 \)`. Therefore, there must be 49 red marbles in the bag.