a person walks at a speed of 4 km / hr and runs at a speed of 8 km / hr . how many hours will the person require to cover a distance of 20 km , if the person completes half of the distance by walking and the other half by running ?
"time = 10 / 4 + 10 / 8 = 30 / 8 = 3.75 hours the answer is c ."
add(divide(divide(20, const_2), 4), divide(divide(20, const_2), 8))