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# Related rates (multiple rates)

AP.CALC: CHA‑3 (EU), CHA‑3.E (LO), CHA‑3.E.1 (EK)
You might need: Calculator

## Problem

The base of a triangle is decreasing at a rate of 13 millimeters per minute and the height of the triangle is increasing at a rate of 6 millimeters per minute.
At a certain instant, the base is 5 millimeters and the height is 1 millimeter.
What is the rate of change of the area of the triangle at that instant (in square millimeters per minute)?