a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 860 in 4 years . the sum is :
"s . i . for 1 year = rs . ( 860 - 815 ) = rs . 45 . s . i . for 3 years = rs . ( 45 x 3 ) = rs . 135 . principal = rs . ( 815 - 135 ) = rs . 680 . answer : option c"
subtract(815, divide(multiply(subtract(860, 815), 3), 4))