Homework Help: math

Posted by mike on Monday, May 21, 2012 at 10:09pm.

find the area of a triangle with the base 1 1/4 and height 4/9 ( Hint the area of a traingle is equals half the product of its base and height ) I came up with .55 or 11/20 is this correct ???

math - Jai, Monday, May 21, 2012 at 10:33pm
No. First to multiply fractions, we change mixed number into improper fraction. The mixed number here is 1 1/4. To change this, we multiply the denominator (the 4) to the constant (the first 1, not the 1 above the bar line) and add this to numerator. thus,
1 1/4 = (1*4 + 1)/4 = 5/4

then recall that the area of triangle is given by
A = (1/2)bh
where b is base and h is height
substituting,
A = (1/2) * (5/4) * (4/9)
to multiply fractions, we just multiply the numerator by numerator & denominator by denominator:
A = (1 * 5 * 4) / (2 * 4 * 9)
A = 20/72
A = 5/18

hope this helps~ :)

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