walking with 4 / 5 of my usual speed , i miss the bus by 5 minutes . what is my usual time ?
"speed ratio = 1 : 4 / 5 = 5 : 4 time ratio = 4 : 51 - - - - - - - - 5 4 - - - - - - - - - ? è 20 answer : d"
multiply(divide(5, divide(5, 4)), 5)