X.

145. Interest Formulas.

The elements involved in computation of interest are the principal, rate, time, interest, and amount.

lint Let p = the principal, r = the interest of $$1$ for $1$ year, at the given rate, t = the time expressed in years, i = the interest for the given time and rate, a = the amount (sum of principal and interest).

146. Given the Principal, Rate, and Time. Find the Interest.

Since $r$ is the interest of $$1$ for $1$ year, $pr$ is the interest of $$p$ for $1$ year, and $prt$ is the interest of $$p$ for $t$ years

i = prt. rint(Formula 1.)

Find the product of the principal, rate, and time.

147. Given the Interest, Rate, and Time. Find the Principal.

lint By formula 1, prt = i. lint Divide by $rt$, p = irt. rint(Formula 2.)

Divide the interest by the product of the rate and time.

148. Given the Amount, Rate, and Time. Find the Principal.

lint From formula 1, p + prt = a, lintor p(1 + rt) = a. lint Divide by $1+rt$, p = a1 + rt. rint(Formula 3.)

Divide the amount by