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No zeros

By David, 20 February 2019 Brainteaser

Which two whole numbers – without any zeros – multiply together to make 1 000 000?

Scroll down for the answer!

 

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Brainteaser answer

A good way to tackle this question is by breaking down 1 000 000 into smaller numbers.

1 000 000 = 10 x 10 x 10 x 10 x 10 x 10

And since 10 = 2 x 5, we know that:
1 000 000 = 2 x 5 x 2 x 5 x 2 x 5 x 2 x 5 x 2 x 5 x 2 x 5

We can reorder these:
1 000 000 = 2 x 2 x 2 x 2 x 2 x 2 x 5 x 5 x 5 x 5 x 5 x 5

And start grouping them again:
1 000 000 = 64 x 5 x 5 x 5 x 5 x 5 x 5
1 000 000 = 64 x 15625

Do you have another way of tackling the problem? Pop it in the comments below!

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2 comments

  1. To answer the problem for 10:
    2 X 5
    Just keep doubling one side and halving the other to still make 10.
    4 X 2.5
    8 X 1.25
    16 X .625
    32 X .3125
    64 X .15625
    If we changed the magnitude of .15625, might we get the numbers we need? Let’s try.
    64 X 15,625 = 1,000,000 Yes!

      Reply
  2. Break it into 100s and then into 25 and 4

      Reply

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