Estimate $\int_0^4 (8 - 2x)\, dx$, the area of the triangle with base 4 and height 8.

16 (answers within ±2 count)

$\int_0^4 (8-2x)\, dx = [8x - x^2]_0^4 = 32 - 16 = 16$. Or: triangle area $= \frac{1}{2} \times 4 \times 8 = 16$.