Exam-Style Question on Probability
A mathematics exam-style question with a worked solution that can be revealed gradually
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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