Question

How many years would it take Jim to earn interest equal to half of his original principal at 10% simple interest?

Answer 1

Now, recall that I = Prt.

now, half of the original principal is just P/2, so, how many years will it take Jim to get in interest, an amount that is half of what he put in.

now.... neverminding P amount, we can say... that say if P = 2, then I = 1, because we want I to be half of P, and when that happens, every $2 returned $1 in interest with a 10% simple interest, what year is it?

$\bf \qquad \textit{Simple Interest Earned}\\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\to &\ 1\\ P=\textit{original amount deposited}\to& \ 2\\ r=rate\to 10\%\to \frac{10}{100}\to &0.10\\ t=years \end{cases} \\\\\\ 1=2\cdot 0.10\cdot t\implies 1=0.2t\implies \quad \cfrac{1}{0.2}=t\implies 5=t$