Workout the simple interest on £530 at 4.5% per annum after six months

530 at 4.5%.
interest rate = 4.5% per year = 0.045
year has 12 months and you want 6 months therefore
12/6 = 0.5 or 2
Multiply them all
530 X 0.045 X 0.5 = 11.93 total interest
530 + 11.93 = 541.93 final amount

20000 as first it increases by 2500 then by 5000 so next it will increase by 10000