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# Grandpa's Rock Cakes

Grandpa has made one of his special giant rock cakes.

At his party, five of the guests tried to guess the weight of the cake.

Their guesses were 5 040g, 5 060g, 5 110g, 5 120g and 5 150g.

Actually, none of them was right. Only two were more than 30 grams out, and those guesses were out by 70g and 90g.

What was the weight of the cake?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

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Age 11 to 14

ShortChallenge Level

- Problem
- Solutions

Grandpa has made one of his special giant rock cakes.

At his party, five of the guests tried to guess the weight of the cake.

Their guesses were 5 040g, 5 060g, 5 110g, 5 120g and 5 150g.

Actually, none of them was right. Only two were more than 30 grams out, and those guesses were out by 70g and 90g.

What was the weight of the cake?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.

You can find more short problems, arranged by curriculum topic, in our short problems collection.

My measurements have got all jumbled up! Swap them around and see if you can find a combination where every measurement is valid.

A recipe for flapjacks calls for a certain quantity of butter, sugar and oats. Given the amount of these ingredients I have, how many flapjacks can I make?

Can you rank these sets of quantities in order, from smallest to largest? Can you provide convincing evidence for your rankings?