find the rate of interest compound semi-annually at which birr 2000 will grow to birr 5000 in 9 years?

let the semi-annual rate be i

2000(1+i)^18 = 5000
(1+i)^18 = 2.5
take the 18th root of both sides
1+i = 2.5^(1/18) = 1.05222
i = .05222

the rate is .10445 or appr 10.445% per annum compounded semi-annually