Question

how long must $217 be invested at a rate of 6% to earn 78.12 dollars and interest

Answer 1

In ths case the answer is very simple.

Step 01:

Data:

p = investment = $217

r = interest rate = 6% = 0.06

I = interest = $78.12

t ( years) = Time = ?

Step 02:

Simple Interest

I = p * r * t

78.12 = 217 * 0.06 * t

$\begin{gathered} \frac{78.12}{217\cdot0.06}=t \\ 6\text{ = t} \end{gathered}$

The answer is:

t = 6 years