## Precalculus (6th Edition) Blitzer

$P=\dfrac{I}{rt}$
Divide $rt$ on both sides of the equation to obtain: $\require{cancel} \dfrac{I}{rt} = \dfrac{Prt}{rt} \\\dfrac{I}{rt} = P \\P=\dfrac{I}{rt}$ This formula gives the principal amount invested. I = interest, r = time, and r = interest rate