The percentage change is computed by
percentage change = ((new value)/(original value) - 1) × 100%
Problems 1–3 all use this formula.
1. (3.25/.99 - 1)×100% ≈ 228.3%
2. (2.75/3.25 - 1)×100% ≈ -15.4%
3. (2.75/.99) - 1)×100% ≈ 177.8%
4. The formula for simple interest is
I = Prt
where P is the principal amount, r is the rate, t is the number of periods, and I is the interest earned. Substitute the given values and solve for t.
400 = 5000·0.04·t
400/200 = t = 2
The money was in the bank for 2 years.