p , q and r together earn rs . 1980 in 9 days . p and r can earn rs . 600 in 5 days . q and r in 7 days can earn rs . 910 . how much amount does r can earn per day ?
"explanation : amount earned by p , q and r in 1 day = 1980 / 9 = 220 - - - ( 1 ) amount earned by p and r in 1 day = 600 / 5 = 120 - - - ( 2 ) amount earned by q and r in 1 day = 910 / 7 = 130 - - - ( 3 ) ( 2 ) + ( 3 ) - ( 1 ) = > amount earned by p , q and 2 r in 1 day - amount earned by p , q and r in 1 day = 120 + 130 - 220 = 30 = > amount earned by r in 1 day = 30 answer : option a"
subtract(add(divide(600, 5), divide(910, 7)), divide(1980, 9))