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Huisang
Huisang asked in Science & MathematicsMathematics · 5 years ago

Why do We count the decimal places when multiplying decimals?

This problem came out on my test.How am I supposed to explain this??

2 Answers

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  • Como
    Lv 7
    5 years ago
    Favorite Answer

    A good way is probably to estimate the answer

    Example

    26 • 73 x 4 will be "round about" 100

    thus

    2 6 • 7 3

    x 4

    ----------------

    1 0 6 • 9 2________will be the answer

    ---------------

  • ?
    Lv 7
    5 years ago

    So you know how many digits there will be after the decimal point in your answer.

    Generally you multiply the two numbers as whole numbers. Then you adjust the result by dividing by the proper power of 10.

    Example:

    2.5 x .8 // 1+1 = 2 decimal places

    25 x 8 = 200 = 200.

    shift decimal point left 2 places

    => 2.00 = 2

    Note that you could do this problem in fractions without using decimals:

    2.5 x .8 = 5/2 x 8/10 = 40/20 = 2

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