Question

The simple interest on an investment of $4000 for one year is $140.

What is the interest rate?

Answer 1

I = PRT....however, since we are looking for R, we can change the equation to this :
I/PT = R
I = 140
P = 4000
T = 1
now we sub
I/PT = R
140/(4000)(1) = R
140/4000 = R
0.035 = R (change to a percent)
3.5% = R

check...
I = PRT
140 = (4000)(.035)(1)
140 = 140 (correct)

Interest rate is 3.5%