Question

Shown below are the steps a student took to solve the simple interest formula A = P(1 + rt) for r.

Answer 1

The student did not distribute properly to get A= P+Prt.

The equation can be fixed by putting a factor of P in the denominator: r=(A-P)/Pt

Explanation:

Answer 2

To solve A = P(1 + rt) for r, first isolate (1 +rt) by dividing both sides of this equation by P:

A/P = 1 + rt.

Next, isolate rt by subtracting 1 from both sides:

A/P - 1 = rt

Finally, divide both sides by t:

A/P - 1

----------- = r

t

This could be written in other formats, such as:

A - P

-------- = r

Pt