Question

There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is 6 over 9 . There are 26 red marbles in the bag and each is equally likely to be chosen. Work out how many marbles in total there must be.



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Answer 1

Answer:

Let B be the amount of Blue marbles and let R be the amount of Red marbles. The probability of choosing a Red marble is:

P(Red) = R/(B+R)

We are told that P(Red) = 2/9; we are also told that B+R = 63. If we substitute these givens into the equation above, we get:

2/9 = R/63

Therefore, R = 63x2/9 = 14.

The amount of Red marbles must be 14.

QED

Answer 2

Answer:

There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is 2/9. There are 63 marbles in total in the bag and each is equally likely to be chosen.

Let B be the amount of Blue marbles and let R be the amount of Red marbles. The probability of choosing a Red marble is:

P(Red) = R/(B+R)

We are told that P(Red) = 2/9; we are also told that B+R = 63. If we substitute these givens into the equation above, we get:

2/9 = R/63

Therefore, R = 63x2/9 = 14.

The amount of Red marbles must be 14.