Question

Fomula: A=1/2(b1+b2)h

A=area of a trapezoid

b1=width at the top

b2-width at the bottom

h=height

A 7-foor tall trapezoid has 42 square feet of area. If is is 9 feet wide at the bottom, how far across is it at the top?

Answer 1

I will set it up for you and you can simplify.

A = 42

h = 7

b2 = 9

I will plug and you can chug.

42 = 1/2(b1 + 9)(7)

Solve for b1, which is read "b sub one."

Can you take it from here?

Answer 2

Thank you for your response. I can set up and calculate. The book says I should be getting 3 feet as my answer. That is not what I am getting.

Answer 3

Here it is:

First multiply 7 x 1/2 = 7/2.

We now have this equation:

42 = 7/2(b1) + 9)

Simplify the right side of the equation and the whole thing becomes


42 = 7/2(b1) + 63/2

Subtract 63/2 from 42.

42 - 63/2 = 10_1/2

We now have:

10_1/2 = 7/2(b1)

10_1/2 divided by 7/2 = b1

3 feet = b1

Done!