Two word problems.

[Guest]

The length of a rectangle is 5 cm more than its width. If the area of the rectangle is 84 cm2, find the dimensions of the rectangle.

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The manager of a bicycle shop has found that the revenue (in dollars) from the sale of x bicycles is given by the following equation.

R = x2- 200x
How many bicycles must be sold to produce a revenue of $12,500?


I've been having trouble with both of these, any help?

 

[Guest]

Never mind about the second one, I solved it and got the right answer!


Now I just have to finish the first one...

 

[tkhunny]

The length of a rectangle is 5 cm more than its width. If the area of the rectangle is 84 cm2, find the dimensions of the rectangle.

Name Stuff!

L = Length of Rectangle
W = Width of Rectangle

"length of a rectangle is 5 cm more than its width"

L = W+5 cm

"the area of the rectangle is 84 cm²"

This is NOT obvioius, unless you happen to know a formula for calculating the area of a rectangle. If you do know such a formula, we're almost done.

L*W = 84 cm²

Substitute from above

(W+5 cm)*W = 84 cm²

That is a crucial step. If you do not understand what just happened there, you will not be able to solve the next problem that comes along. The concept of "Simple Substitution" is VERY IMPORTANT.

OK, now what?

 

[pav]

a=l*w


take the length x

width = x+5

x(x+5)=84

x^2+5x-84=0

(x+12)(x-7)

im sure you can do the rest find x and plug in to get the dimesnsions