the speed of the train is 60 miles per hr...
so in 2 hrs, it will cover (60 * 2) = 120 miles
and in 4 hrs, it will cover (60 * 4) = 240 miles
so the train covered 120 more miles in 4 hrs then it did in 2 hrs....or the train covered twice as many miles in 4 hrs as it did in 2 hrs