Find the rate percent per annum simple interest for K420 to be the interest on K1200 invested for 5 years.

The formula for simple interest is $I = P \times R \times T$, where $I$ is the interest, $P$ is the principal, $R$ is the annual interest rate, and $T$ is the time in years.
Given:
Interest ($I$) = K420
Principal ($P$) = K1200
Time ($T$) = 5 years

Refer to the given information to answer Questions 4 and 5
K8 000 is invested for 12 years at 12% pa. The interest is compounded half-yearly.

4. Calculate the amount after 12 years.

The formula for compound amount is $A = P \left(1 + \frac{R}{n}\right)^{nt}$, where $A$ is the amount, $P$ is the principal, $R$ is the annual interest rate, $n$ is the number of times interest is compounded per year, and $t$ is the time in years.
Given:
Principal ($P$) = K8 000
Annual interest rate ($R$) = 12% = 0.12
Time ($t$) = 12 years
Compounding frequency ($n$) = 2 (half-yearly)

5. Calculate the interest earned after 12 years.

Amount ($A$) = K32391.24
Principal ($P$) = K8 000

6. Evaluate: K5 000 $(1 + 17\%)^5 =$