a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 894 in 4 years . the sum is :
"s . i . for 1 year = rs . ( 894 - 815 ) = rs . 79 . s . i . for 3 years = rs . ( 79 x 3 ) = rs . 237 . principal = rs . ( 815 - 237 ) = rs . 578 . answer : option e"
subtract(815, divide(multiply(subtract(894, 815), 3), 4))