#### Problem 21E

21. The altitude of a triangle is increasing at a rate of $1 \mathrm{~cm} / \mathrm{min}$ while the area of the triangle is increasing at a rate of $2 \mathrm{~cm}^{2} / \mathrm{min}$. At what rate is the base of the triangle changing when the altitude is $10 \mathrm{~cm}$ and the area is $100 \mathrm{~cm}^{2}$ ?