<PRE><B>Question 109857</B>
The area of a trapezoid is 186 in squared. If the height is 11 in. and the longer base is 21 in., what is the length of the shorter base? Round your answer to the nearest tenth.
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The formula
A = {{{1/2}}}*h*(a+b)
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Solve for a (the shorter side)
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Mult equation by 2 to get rid of the fraction: 
h(a+b) = 2A
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Divide both sides by h:
a + b = {{{(2A)/h}}}
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Subtract b from both sides
a = {{{(2A)/h}}} - b
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Substitute the given values in the above equation:
a = {{{(2*186)/11}}} - 21
:
a = {{{372/11}}} - 21
:
a = 33.8 - 21
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a = 12.8 is the shorter side
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Check solution:
A = {{{1/2}}}*11(12.8+21)
A = {{{1/2}}}*11(33.8)
A = {{{1/2}}}*371.8
A = 185.9 ~ 186</PRE>