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| Math Central | Quandaries & Queries |
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Question from Nikheel, a student: Amar baked a cake. john ate 1/6 of the cake. susan ate 1/5 of what was left. chan ate 1/4 of what was left. cindy ate 1/3 of what was left. luigi ate 1/2 of what was left. how much of the original cake was left. |
Hi Nikheel.
Start with a whole cake (mine is round).
1. John ate 1/6 of it. So divide it into 6 pieces and take one away.
This leaves (5/6 of the cake).
2. Susan ate 1/5 of what was left. So divide what is left into 5 pieces and take one away.
This leaves 4/5 of 5/6 of the cake = 4/5 x 5/6 = 4/6 of the cake.
3. Continue this process until you find out how much is left. The key is to multiply the fractions, simplifying (cancelling) as you go.
Cheers,
Stephen La Rocque.
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