Question

The simple interest on a certain sum for 5 years at 8% per annum is $ 120 more than the simple interest on the same sum for 3 years at 10% per annum, find the sum.

Answer 1

$si = ptr \div 100$
let the sum be p,

p(5*8/100) = p(3*10/100) + 120
p(0.4) = p(0.3) + 120
p(0.4) - p(0.3) = 120
p(0.1) = 120
p = 120/0.1
p = $1200