Math

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Is there a trick or formula or easy way to figure out square root mentally?

  • Math -

    Memorize the common square roots

    2 * 2 = 4
    3 * 3 = 9
    etc.

    Then using those squares, you can estimate other square roots.

    Example:

    square root of 130 =

    √ 121 = 11
    √ 144 = 12

    √ 130 is between 11 and 12

  • Math -

    Ok. Is there an easy way to figure the perfect square root for numbers 13 through 25.

  • Math -

    3 * 3 = 9
    4 * 4 = 16
    5 * 5 = 25

    Memorize the squares of 1 - 12

  • Math -

    So are u saying to memorize the squares for 13 - 25 as well? Not sure if my question is clear. For e.g. square of 23 is 529. By multiplying the last digit of 23 ( 3x3)= 9, same last digit of the number 529, is there a way I easily work out the first 2 numbers 52?

  • Math -

    ahh, so you want to square the numbers , not take their square roots

    A mental way to multiply any two 2-digit numbers
    e.g.
    34 x 34
    4x4 = 16 , so the last digit is 6 , with 1 to carry
    3x4+ 4x3 = 24 plus the one to carry is 25
    so the tens digit is 5 , with 2 to carry
    3x3 = 9 with 2 to carry is 11

    so 34^2 = 1156

    the numbers don't have to be the same ...

    e.g. 56 x 83
    6x3 = 18 , so unit digit is 8 , carry 1
    5x3 + 6x8 = 63 , so tens digit is 4 , carry 6
    5x8 = 40, plus the carry 6 = 46

    56x83 = 4648

    but really, am I not just doing the steps of ordinary multiplication ??

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