Trapezoid Area 1.375 cm²: Find the Red Side Length

Question

The area of the trapezoid in the diagram is 1.375 cm².

Work out the length of the side marked in red.

00:09 Let's find A B.

00:12 We'll use the trapezoid area formula.

00:16 Add the lengths of the bases, A B and D C, multiply by the height, H, and then divide by 2.

00:25 Now, substitute the given values to solve for A B.

00:38 Multiply both sides by 2 to clear the fraction.

00:54 Next, multiply by the reciprocal.

01:03 Isolate A B to find its value.

01:14 And that's how we solve the problem!

The area of the trapezoid will be equal to: $S=\frac{(AB+DC)}{2}\times h$

We insert the available data into the formula:

$1.375=\frac{AB+4}{2}\times0.5$

We then multiply by 2 in order to remove the fraction:

Lastly we again multiply by 2:

$5.5=AB+4$

$5.5-4=AB$

$1.5=AB$

$1.5$ cm