Math

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The area of a rectangle is 90m 2. The base is three less than three times the height. What is the perimeter?

  • Math -

    b = 3 h -3
    area = b h = (3 h - 3)h = 3 h^2 - 3 h = 90
    so
    3 h^2 - 3 h - 90 = 0
    (h+5)(3h-18) = 0
    h = 6 is positive real solution
    so
    b = 3*6 -3 = 15
    then perimeter = 2 h + 2 b

  • Math -

    dont get it

  • Math -

    how did you get that. not rudely.

  • Math -

    Let B = base and H = height

    From the first sentence:

    B * H = 90

    From the second sentence:

    B = 3H - 3

    Substitute the value of B from the second equation into the first and solve for H. Put the value of H in the second equation to find B. Check by putting both values into the first equation.

    As Damon says, "then perimeter = 2 h + 2 b".

    I hope this helps. Thanks for asking.

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