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Grandpa's Rock Cakes
Age 11 to 14
ShortChallenge Level 
The cake weighed 5 130g.
The range of the guesses (5 040g, 5 060g, 5 110g, 5 120g and 5 150g) is 110 so the two 'wild' estimates must both be low or both high.
Since the difference between 5 040 and 5 060 is 20, 5 040 is 90 out and 5 060 is 70 out.
The range of the guesses (5 040g, 5 060g, 5 110g, 5 120g and 5 150g) is 110 so the two 'wild' estimates must both be low or both high.
Since the difference between 5 040 and 5 060 is 20, 5 040 is 90 out and 5 060 is 70 out.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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