A car from a city to B city, 42 meters per hour, 5 hours to B city. Return 45 kilometers per hour, how many hours to a city? It's better to write it clearly!

A car from a city to B city, 42 meters per hour, 5 hours to B city. Return 45 kilometers per hour, how many hours to a city? It's better to write it clearly!

The total distance: 42 × 5 = 210 (meters) return time: 210 ／ 45 = 4 hours and 40 minutes

Uncle Wang traveled 25% of the whole journey in the first hour from city a to city B. after 45% of the journey in the second hour, he was 900 meters away from city B. how many kilometers are there between city a and city B?

A: the distance between the two cities is 6 km

Uncle Liu's car line takes 5-7kg for 12km. Now uncle Liu wants to send a friend to the airport. The distance is 20km. How many kg of gasoline do you need?

5/7*(40/12)
Why 40? Because my uncle is coming back