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 = 9kmTotal time = 1 hFor 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/hspeed s = distance d/time t s = d/tt = 9/(2x 2) 1 = 9/(2x 2)2x 2 = 92x = 7x = 7/2 = 3.5 km/hTherefore the speed for the 4 km = 3.5 km/hSince 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, my did not seem right. Please I need help. Thank you.