An amount of $4000 is invested. the interest rate is 2%. what is the amount earned in one year ?

Interest = PRT/100
Compound interest = P(1 + (R/100))^T

Where P = Principle ( amount )
R = Rate
T = Time

Since the time is only 1 year, the answer will be the same for both interest and compound interest formulae.

∴ 4000(2)(1)/100 =$80 (This is the interest value)

Note if question ask you what is the total amount after x years, be sure to add the interest with the principle.