Problem: excluding stoppages , the speed of a bus is 80 km / hr and including stoppages , it is 70 km / hr . for how many minutes does the bus stop per hour ?
Rationale: "due to stoppages , it covers 10 km less . time taken to cover 10 km = 10 / 80 * 60 = 8 min . answer : c"
annotated_formula: multiply(const_60, divide(subtract(80, 70), 80))