How to Solve Hannah’s Sweets GCSE Math Problem on Probability

Friday, June 5th, 2015


How-to-Solve-Hannah's-Sweet-GCSE-Math-Problem-on-Probability-Blog

Social Media is at it again. And this time it is a simple probability question. It is pretty basic in nature. The story in the question takes a turn to probability towards the end which is probably what surprised a lot of people. Well, decide for yourself.

The actual question

There are n sweets in a bag. 6 of the sweets are orange. The rest of the sweets are yellow.

Hannah takes a random sweet from the bag. She eats the sweet.

Hannah then takes at random another sweet from the bag. She eats the sweet.

The probability that Hannah eats two orange sweets is 1/3.

Show that n² – n – 90 = 0.

Video Solution to Hannah’s Sweets GCSE Math Problem on Probability

If you want a quick and dirty solution (basically something that can come in a tweet):
(6/n)*(5/(n-1)) = 1/3
=> 6*5*3 = n(n-1)
=> 90 = n² – n
=> n² – n – 90 = 0

Tweet this solution

Hope you enjoyed it and learnt from it. Do share it with your friends on facebook and / or tweet it to your followers.

Cheers,
Ravi Handa

How to Solve Hannah’s Sweets GCSE Math Problem on Probability

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