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Multiplying Decimals to Make a Whole Number Product

Directions: Using the digits 1 to 9, at most one time each, fill in the boxes to make a whole number product.

Hint

Hint

How can we tell if it is even possible to make a whole number product?
What digits would be better or worse choices for making a whole number product?

Answer

Answer

The one known answer so far is 9.6 x 8.75 which has a product of 84.

Source: Owen Kaplinsky

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9 comments

  1. another one… 9.6 x 1.25 = 12

  2. Thanks! I’ll add it to the answer key.

  3. Hi
    If you think about multiplying integers, you need the product to have a factor of 1000. I.e. you need prime factors of the multipliers to include 5^3 and 2^3. Additionally, the factors of 5 and 2 must stay in separate multipliers otherwise one would have to end in zero which is not allowed.
    So possible numbers that would work are:
    1.6,2.4,3.2,4.8,5.6,6.4,7.2,9.6
    multiplied by
    1.25,3.75,6.25,8.75
    Any combination of these will work, if the digits are unique.

  4. 3.75 X 4.8 =18 Also Works

  5. Please update answer – I thought there was only one solution then looked in the comments.

  6. 6.25 x 4.8 = 30

  7. 1.6 x 3.75 = 6

  8. I got an answer of 1.25 x 4.8 = 6

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