what is the rate percent when the simple interest on rs . 4000 amount to rs . 640 in 2 years ?
"interest for 1 year = 640 / 2 = 320 interest on rs 4000 p / a = 320 interest rate = 320 / 4000 * 100 = 8 % answer : b"
divide(multiply(const_100, 640), multiply(4000, 2))