A man runs a distance of 9km at a constant speed for the first 4km and then 2km/h faster for the rest of the distance. The whole run takes him one hour. His average speed for the first 4km is what? Total distance = 9km Total time = 1 h For the 1st for 4km, he moved at a constant speed. For the last 5km, his speed was increased by 2km/h. Let the costant speed at 4km be xkm/h. At the last 5km, his speed became (x + 2) km/h. The total speed for the whole runs took him [(x+2) + x] km/h = (2x + 2) km/h speed s = distance d/time t s = d/t t = 9/(2x + 2) 1 = 9/(2x + 2) 2x + 2 = 9 2x = 7 x = 7/2 = 3.5 km/h Therefore the speed for the 4 km = 3.5 km/h Since the speed was increased by 2km/h, that means the speed for the last 5 km/h would become (3.5 + 2) = 5.5 km/h. But when I checked, my answer did not seem right. Please I need help. Thank you.