A bus started out going 20 miles per hour on the highway. One hour later it drove 40 miles per hour on the freeway. How long did it take to go 140 miles? Is the correct answer 3.5 minutes.

To find the time it took for the bus to travel 140 miles, we need to calculate the time for both scenarios separately and then add them together.

First, let's calculate the time it took for the bus to travel the first 20 miles at a speed of 20 miles per hour. We can use the formula:

Time = Distance / Speed

The distance is 20 miles, and the speed is 20 miles per hour. Therefore, the time taken for the first scenario is:

Time = 20 miles / 20 miles per hour = 1 hour

Next, let's calculate the time it took for the bus to travel the remaining 120 miles at a speed of 40 miles per hour. Again, using the formula:

Time = Distance / Speed

The distance is 120 miles, and the speed is 40 miles per hour. Therefore, the time taken for the second scenario is:

Time = 120 miles / 40 miles per hour = 3 hours

Finally, we add the times from both scenarios to find the total time taken by the bus to travel 140 miles:

Total Time = Time for the first scenario + Time for the second scenario
= 1 hour + 3 hours
= 4 hours

So, the correct answer is that it took the bus 4 hours to travel 140 miles.

The answer of 3.5 minutes that you suggested is incorrect.