The railway between north and south cities is 357 kilometers long. The express train leaves from the north city and the local train leaves from the south city. After three hours of rendezvous, the express train runs at an average speed of 79 kilometers per hour. How many kilometers is the local train less than the express train?

Solution 1, [357-(79×3)]3

=[357-237]÷3

= 120÷3

=40 km

That is, the average speed of the local train is 40 kilometers per hour.

As we all know, the express train travels at an average speed of 79 kilometers per hour.

How many kilometers does the local train travel less than the express train per hour on average?

79-40=39 km

Attendant: On average, the local train travels 39 kilometers less per hour than the express train.

Solution 2,79-(357 ÷ 3-79)

=79-( 1 19-79)

=79-40

=39 km

A: (ditto)

Solution 3. Let the local train travel an average of x kilometers per hour.

79×3+3x=357

3x=357-237

3x= 120

X = 40km

79-40=39 km