Question

find the missing length of the following figure (the area of the figure is $8\\ mm^2$) and write your result in the empty box.
answer: \boxed{} mm.
(there is a triangle with a height of 4 mm and base length denoted as $a$)

Explanation:

Step1: Recall triangle area formula

The area of a triangle is $A = \frac{1}{2} \times base \times height$

Step2: Substitute known values

Substitute $A=8$, $height=4$ into the formula:
$8 = \frac{1}{2} \times a \times 4$

Step3: Simplify and solve for $a$

First simplify the right-hand side: $\frac{1}{2} \times 4 = 2$, so $8 = 2a$.
Then solve for $a$: $a = \frac{8}{2} = 4$

Answer:

4 mm.