Jack and Bob travelled from Town F to Town G at constant speeds of 40 mph and 45 mph respectively at the same time. Some time later, they were 20 miles apart. How long had they been travelling?
Since Jack and Bob were traveling at the same direction at the same time, distance between them would be larger and larger as time went on.
Recall the formula: Time = Distance difference ÷ Speed difference
Their speed difference: 45 - 40 = 5 mph
Their distance difference: 20 miles
Thus, the time: 20 ÷ 5 = 4 h