a person can row at 9 kmph and still water . he takes 4 1 / 2 hours to row from a to b and back . what is the distance between a and b if the speed of the stream is 1 kmph ?
"let the distance between a and b be x km . total time = x / ( 9 + 1 ) + x / ( 9 - 1 ) = 4.5 = > x / 10 + x / 8 = 9 / 2 = > ( 4 x + 5 x ) / 40 = 9 / 2 = > x = 20 km . answer : e"
divide(multiply(multiply(subtract(9, 1), add(9, 1)), 4), add(add(9, 1), subtract(9, 1)))