2/5+1/4=8/20+5/20=(8+5)/20=13/20 of the pole climbed in the first two hours, leaving (20-13)/20=7/20 of the pole to climb. The LCM of 4 and 5 -s 4*5=20 because they have no common factors. 1/5 of 20 is 4 so 2/5 of 20 is 8;1/4 of 20 is 5. Therefore 4/20=1/5, 8/20=2/5 and 5/20=1/4.