Michael borrows money from his uncle, who is charging him simple interest using the formula I=prt. to figure out what the interest rate, r, is, Michael rearranges the formula to find r his new formula is r equals

Since the original is Interest equals price times rate times time, taking out rate still includes price times time. So, you first have R = pt. Now to insert interest, you would have to divide the interest by pt, since you invert the multiplying of Rate. So, it would be R = I/pt. Basically, this is used for finding any of the prt segment. For P, use P = I/rt. For T, use T = I/pr. And for Michael's case, to find Rate you use R = I/pt.