Jack and Gary started jogging from point A to point B at the same time. When Jack reached point B in 2 hours, Gary had only completed 90% of the journey. Given than the speed difference between Jack and Gary was 0.8 km/h, find the distance from point A to point B.
Since the spreed difference is 0.8 km/h, 0.8 km * 2 = 1.6 km. They are 1.6 km apart after 2 hours.
You have already solved half of the problem !
Let the distance between A and B ==D
2 x 0.8 ==1.6 km still to jog by the slower jogger.
D - 0.90D ==0.10D km still to jog
D ==1.6 / 0.10 ==16 km - the distance between A and B
Check: 16 / 2 ==8 km/h - speed of the first jogger. 8 - 0.8 ==7.2 km/h speed of the 2nd jogger. 16/7.2 ==2 2/9 - hours - time of the 2nd jogger. 8 km/h x 2 hours ==7.2 km/h x 2 2/9 hours ==16 km.