Homework Help: Algebra

Posted by G on Friday, February 15, 2008 at 10:59am.

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?

Algebra - Guido, Friday, February 15, 2008 at 11:05am
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?
- Algebra - G, Friday, February 15, 2008 at 11:09am
  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.
  - Algebra - Guido, Friday, February 15, 2008 at 11:13am
    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!

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