Answer:
Half a year (6 months)
Explanation:
Simple interest is based on the principal amount of a loan or deposit, whereas compound interest is based on the principal amount and the interest that accumulates on it in every period.
Simple Interest = P x r x n
where P = Principal amount, r = Annual interest rate, n = Term, in years
9% = 9 ÷ 100 = 0.09 so r = 0.09
Therefore,
Simple Interest = P x r x n
8100 = 180000 x 0.09 x n
8100 = 16200n
n = 0.5
Therefore, he will earn N8100 in interest on an initial investment of N180,000 at 9% simple interest over half a year