Question

A= P(1 + rt)

A= P+rt
A - P= rt
r= (A- P)/t
Explain the algebraic error in the student's work.
Then, state how the equation r = (A- P)/t can be
modified to produce the correct result.

Answer 1

The student forgot to distribute the P into rt as well in the second line.

So, to solve for r correctly:
A=P(1+rt)
A=P+Prt
A-P=Prt
r=(A-P)/Pt