Problem: walking with 4 / 5 of my usual speed , i miss the bus by 7 minutes . what is my usual time ?
Rationale: "speed ratio = 1 : 4 / 5 = 5 : 4 time ratio = 4 : 51 - - - - - - - - 7 4 - - - - - - - - - ? è 28 answer : c"
annotated_formula: multiply(divide(7, divide(5, 4)), 5)