99.9% failed – The answer to 3=18, 4=32 …revealed

Thanks to those of you who took part in the little maths problem last week. It was interesting to see the variety of answers coming out. I’m not sure how the first 3 were calculated, but I will try to explain some of the other ones…

1) 150

2) 180

3) 20

4) 152 because the units have a pattern 8, 2, 0, 2 and tens goes up sequentially by 2 – 1, 3, 5, 7. This give 8 = 112, 9 = 130, 10 = 152

5) 116 because 3 + 7 = 10, therefore 10 = 18 + 98 = 116

6) 100 because 5 + 5 = 10 therefore 10 = 50 + 50 = 100

7) 104
because 4 + 6 = 10 therefor 10 = 32 + 72 = 104

8) 10 clearly 10 = 10

9) And the most popular (so clearly wrong?) was 200 because the pattern is 10 * 10 * 2 = 200

UPDATED 25/01/2014 due to additional possibilities:
10) 62. To get this, you need to remove the equals sign and calculate the difference between the numbers – this difference increases by 4 between each pair of numbers. So, 432 – 318 = 114, 550 – 432 = 118, 672 – 550 = 122, 798 – 672 = 126. The next number will be 798 + 130 = 928, 928 + 134 = 1062. Now reinstate the = to give 10=62. Phew. Thanks to Tony Bialorucki for this answer.

11) ?. Yes question mark. If you read it as a set of statements rather than a question, then 10=?. Thanks to sik for this answer.

There are several issues with how this problem is written, which means you could end up with almost any answer given the correct logic –
First, it starts off with a statistic (99.9%) which is to entice you attempt an answer.
Second, the question itself is not correctly worded. It should go along the lines of ‘Complete the following sequence…’
Thirdly, the calculations are clearly all incorrect, so you could almost put any number down. The logic is deliberately vague

When I originally did this problem, my first answer was 160. This was because I didn’t read the question properly (a problem my 9 year old often has), and assumed it was asking for the next number in the sequence – 8 = 160!

So, what is the answer?

It’s 200, although I did like the 10 from The Penguin as this is the only answer which is true!

Sorry if anyone was disappointed, but hope you enjoyed the problem.

Like this post? Then check out more great maths books on Amazon

12 thoughts on “99.9% failed – The answer to 3=18, 4=32 …revealed

  1. Michael Shafer

    I disagree, as it did not state this was a sequence. All you had to go on were the initially stated “givens”. My vote is 116 as the correct answer.

    Reply
  2. US NAVY

    For me the answer, which is not in your list, was 400

    10 = 2 x 5 = 8 x 50 = 400

    Pre requirements are:
    2 = 8 = 2×4 (following the sequence below number 3)
    5 = 50 = 5×10

    Reply
      1. [email protected]

        I recieved 200 by another means.

        3=18
        add 14
        4=32
        add 18 (goes up by 4)
        5=50
        add 22 (goes up by 4)
        6=72
        add 26(goes up by 4)
        7=98
        add 30
        8=128
        add 34
        9=162
        add 38
        10=200
        HOWEVER this only works from 3 on. Not 2 or 1

        Reply

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