Posted by **Josh** on Monday, February 23, 2009 at 6:58pm.

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

- Math -
**Damon**, Monday, February 23, 2009 at 7:38pm
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 -
**Josh**, Monday, February 23, 2009 at 7:54pm
dont get it

- Math -
**Josh**, Monday, February 23, 2009 at 8:06pm
how did you get that. not rudely.

- Math -
**PsyDAG**, Tuesday, February 24, 2009 at 10:36am
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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