train a leaves station traveling at 40 mph Eight hours later

train a leaves station traveling at 40 mph. Eight hours later train b leaves the same station traveling in the same direction at 60mph. how long does it take for train b to catch up to train a?

Solution

In 8 hours, train A has gone 320 miles (40*8)
Train B gains on train A at 20 mph (60-40).
320 miles/20 mph = 16 hours.