(98)^2 no calculator mental math

Discussion in 'Calculator Requests' started by math_celebrity, Jan 5, 2024.

  1. math_celebrity

    math_celebrity Administrator Staff Member

    Round 98 to the nearest 10. This is 100. Call this a.

    Calculate b which is a - our original number:
    b = 100 - 98
    b = 2

    We can use this formula:
    (a - b)^2 = a(a- 2b) + b^2

    Given a = 100 and b = 2, we have:
    (100 - 2)^2 = 100(100 - 2(2)) + 2^2
    98^2 = 100(96) + 4
    98^2 = 9600 + 4
    98^2 = 9,604

     

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