Question

I need help with the question attached I’m u sure how to complete the question

Answer 1

In simple interest, we can use the formula:

`I=P\cdot r\cdot t`

Where P is the principal value, that is, the value of the loan, $9000; r is the annual rate and t is the period of loan in years.

We know Rita paid interest of $336, so

`I=336`

However, the period that she had is not in years, it is in months. However, in simple interest we can just convert "t" from year to months. If she got 7 months, this is equivalent of 7/12 years, because one year has 12 months.

Thus, t = 7/12

Now, we know "I", "P" and "t", we can substitute and solve for "r":

`\begin{gathered} 336=9000\cdot r\cdot(7)/(12) \\ (336)/(9000)=r\cdot(7)/(12) \\ 0.037333\ldots=r\cdot(7)/(12) \\ r=(12)/(7)\cdot0.037333\ldots \\ r=(0.448)/(7)=0.064 \end{gathered}`

In percentage, we have 6.4% of annual interest.