if a car went the first third of the distance at 80 kmh , the second third at 18 kmh , and the last third at 48 kmh , what was the average speed of the car for the entire trip ?
"assume d / 3 = 720 ( this number is convenient because it is divisible by 80 , 18 and 48 ) so : 720 = 80 * t 1 = 9 hrs 720 = 18 * t 2 = 40 hrs 720 = 48 * t 3 = 15 hrs t = t 1 + t 2 + t 3 = 64 hrs d = rt ( 720 * 3 ) = r * 64 r = 33.75 answer : a"
divide(const_3, add(add(divide(const_1, 80), divide(const_1, 18)), divide(const_1, 48)))