# Exam-Style Question on Probability

## A mathematics exam-style question with a worked solution that can be revealed gradually

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Question id: 165. This question is similar to one that appeared on a GCSE Higher paper (specimen) for 2017. The use of a calculator is not allowed.

A box contains only green and yellow crayons.

Luka takes one crayon at random from the box. The probability that she takes a green crayon is $$\frac16$$.

Luka returns the crayon to the bag and adds four more green crayons to the box. The probability that she takes one green crayon at random is now $$\frac14$$.

How many crayons of each colour were originally in the box?

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