Answer:
10 mm
Step-by-step explanation:
You can find the missing dimension using the triangle area formula with the dimensions you know.
A = 1/2bh
40 mm² = 1/2(b)(8 mm)
b = 40 mm²/(4 mm) = 10 mm . . . . . . . divide by the coefficient of b
The triangle's base is b = 10 mm.
