SOLUTION: If the length of the base of a triangle is increased by 10 percent and the height is decreased by 20 percent, what is the percent decrease in the area of the triangle?

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Question 366099: If the length of the base of a triangle is increased by 10 percent and the height is decreased by 20 percent, what is the percent decrease in the area of the triangle?
Answer by fractalier(6550) About Me  (Show Source):
You can put this solution on YOUR website!
We can express the original area of a triangle as
A+=+%281%2F2%29bh
If the new base is 10% greater, the new b is (1.1)b.
If the new height is 20% less, the new h is (0.8)h.
Now substituting, we get
A+=+%281%2F2%29%281.1%2Ab%29%280.8%2Ah%29 =
A+=+%281%2F2%29%28.88%29bh
Notice how the original area is only 88% of what it was...
So there was a 12% decrease in area.