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Difficulty: Extreme!

George bought a bag of 70 lollies on Monday. He didn’t eat many on Monday, but he really liked the flavour. Every day after that he ate three more lollies than he had the previous day. The next Monday, George was about to eat his first lolly for the day and noticed the bag was empty.

How many lollies did George eat on the first Monday?

Scroll down or click for a hint, or the answer!

 

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Brainteaser hint

George ate 70 lollies in 7 days, which is an average of 10 sweets a day. Try making an estimate based on this statistic.

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Brainteaser answer

George’s sweet consumption increases at a steady rate, so he would have eaten about 10 sweets on the middle day (Thursday). Monday is three days before Thursday so he would have eaten 3 x 3 = 9 fewer sweets on Monday. That would mean he ate only one sweet!

To check this estimate, George ate:
1 (Monday) + 4 + 7 + 10 (Thursday) + 13 + 16 + 19 (Sunday) = 70 sweets

2 responses

  1. allan Kreuiter Avatar
    allan Kreuiter

    Not a good question, you said ‘them’ which has a specific plural meaning,
    ie not one
    you could have just said “the flavour” or made the total 77?
    you also missed the chance of solving it by taking (7×3) away from 70 leaving 52 and talking about sequences in maths, a cleverer solution than using averages in this case

  2. David Shaw Avatar
    David Shaw

    Hi allan,
    Happy to change the wording of the question.
    There are many good ways to solve this problem – I’m glad you found your own!

    Cheers,

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