The area formula of a trapezoid is given \(A=h\left(\frac{b_1+b_2}{2}\right)\)
The problem also tells you the following information:
A = unit of area (in a square unit like square feet)
b_1 = one base
b_2= other base
h = perpendicular height
The order in which you substitute the bases are immaterial in this case since addition abides by the commutative and associative properties.
If the questions asks for "how many square feet," this is the unknown. Square feet is indeed a unit of area, so this would be A in the formula above. We don't know what "A" is yet, but we will solve for it. The question directly states the other variables' meaning.
A = unknown area in square feet
b1= 125ft
b2 = 81ft
h = 75ft
All this information has been nicely synthesized, and we have established the meaning of every single variable in the original formula. Now, we must use the formula to figure out the unknown or the area in square feet:
\(A=h\left(\frac{b_1+b_2}{2}\right)\) | We know what the variables equal already, so plug them in. |
\(A=75\text{ft}*\frac{125\text{ft}+81\text{ft}}{2}\) | Now it is a matter of simplifying. |
\(A=75\text{ft}*\frac{206\text{ft}}{2}\) | |
\(A=75\text{ft}*103\text{ft}\) | It is imperative to remember that multiplying two common units result in that unit squared. It is just like multiplying common variables together. |
\(A=7725\text{ft}^2\) | |