Question

$18, P = $200, r = ?, t = 1.5 years. Find the annual interest rate.

Answer 1

                                                  Question 1)

Given

Interest I = $18

Principle P = $200

t = 1.5 years

To determine

Interest rate r = ?

Using the formula

$P = Irt$

$r=\frac{I}{Pt}$

susbtituting I = 18, t = 1.5 and P = 200

$r=\frac{18}{\left(200\times 1.5\right)}$

$r = 0.06$

or

r = 6%       ∵ 0.06 × 100 = 6%

Therefore, we conclude that the interest rate required to  accumulate simple interest of $18.00  from a principal of $200 over 1.5 years is 6% per year.

                                                    Question 2)

Given

Interest I = $60

Principle P = $750

Interest rate = 4% = 0.04

To determine

Time period t = ?

Using the formula to calculate the time period

$P = Irt$

$t\:=\:\frac{P}{Ir}$

$t=\frac{60}{\left(750\times 0.04\right)}$

$t = 2$ years

Therefore, the time required to  accumulate simple interest of $ 60.00

from a principal of $ 750 at an interest rate of 4% per year  is 2 years.