Two years ago, Kim Ean invested RM P in her account which earns r% simple interest. After 18 months, she noticed that the amount had become RM 10,450 and today, the amount is RM 10,600. Find the value of r.

Answer 1

Since the interest appears to be applied monthly, use 1/12 the annual rate. After n months,
A = P(1 + n*r/12100)
Now use the given data
P(1+18r/1200) = 10450
P(1+24r/1200) = 10600
Dividing #2 by #1, we have
(1+24r/1200)/(1+18r/1200) = 10600/10450
r = 3%

Answer 2

Two years ago, Khaled invested RM P in his account which earns r% simple interest.
After eighteen months, he noticed that the amount had become RM10450 and today the
amount is RM 10600. Find the value of P and r.