Question

Find the missing b for a trapezoid with a=68, h=4, b=21

Answer 1

We will have to use the formula for the area of a trapezoid on this problem, which is ($b_1$ and $b_2$ are the bases of the trapezoid and $h$ is the height):

$\dfrac{b_1 + b_2}{2} \cdot h$

All we need to do is substitute the information we are given into our formula:

$\dfrac{21 + b_2}{2} \cdot 4 = 68$

Now, let's just simplify the equation:

$\dfrac{21 + b_2}{2} \cdot 4 = 68$

$\dfrac{21 + b_2}{2} = 17$

$21 + b_2 = 34$

$b_2 = 13$

The missing base has a length of 13 units.