a can contains a mixture of liquids a and b is the ratio 7 : 5 . when 12 litres of mixture are drawn off and the can is filled with b , the ratio of a and b becomes 7 : 9 . how many liter of liquid a was contained by the can initially ?
"ci * vi = cf * vf ( 7 / 12 ) * ( v 1 - 12 ) = ( 7 / 16 ) * v 1 ( v 1 - 12 ) / v 1 = 3 / 4 12 accounts for the difference of 1 on ratio scale so initial volume = v 1 = 4 * 12 = 48 litres . 7 / 12 of the initial mixture was liquid a so liquid a was ( 7 / 12 ) * 48 = 28 litres . answer : d"
multiply(7, divide(multiply(add(7, 12), subtract(12, multiply(divide(5, add(7, 5)), 12))), subtract(multiply(12, 7), multiply(7, 5))))