SOLUTION: The height of a triangle is 2 millimeter less than the base. If the area is 60 square millimeters, find the base

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Question 156797: The height of a triangle is 2 millimeter less than the base. If the area is 60 square millimeters, find the base
Found 2 solutions by nerdybill, jojo14344:
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
The height of a triangle is 2 millimeter less than the base. If the area is 60 square millimeters, find the base
.
Remember that the area of any triangle is:
area = (1/2)hb
where
h is height
b is base
.
If we
Let b = base
then
Your problem gives:
height = b-2
area = 60 sq mm
.
Plugging it all into:
area = (1/2)hb
60 = (1/2)(b-2)b
120 = (b-2)b
120 = b^2 - 2b
0 = b^2 - 2b - 120
.
factoring:
0 = (b-12)(b+10)
b = {12, -10}
we can throw out the negative solution since it doesn't make sense for a "measurement".
.
Therefore,
base is 12 millimeters

Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!
We know Area%5BT%5D=%281%2F2%29bh Sustituting when h=b-2, height is 2mm less than the base
60=%281%2F2%29%28b%29%28b-2%29------------------------> working eqn
60=%281%2F2%29%28b%5E2-2b%29, cross multiply
120=b%5E2-2b ---> b%5E2-2b-120=0
Solve by QUADRATIC, a=1, b=-2, & c=-120
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x=%28-%28-2%29%2B-sqrt%28-2%5E2-4%2A1%2A-120%29%29%2F%282%2A1%29
x=%282%2B-sqrt%284%2B480%29%29%2F2=%282%2B-sqrt%28484%29%29%2F2
x=%282%2B-22%29%2F2
2 values: x=%282%2B22%29%2F2=24%2F2=12mm BASE
x=%282-22%29%2F2=%28-20%2F2%29=%28-10mm%29, DON'T USE
In doubt? Go back working eqn:
60=%281%2F2%29%2812%29%2812-2%29
60=%281%2F2%29%2812%29%2810%29
60=%281%2F2%29%28120%29
60=60
Thank you,
Jojo