A car from a to B, 60 kilometers per hour, took 12 hours, this car back speed?

A car from a to B, 60 kilometers per hour, took 12 hours, this car back speed?

60 km / h

How many hours can a car return to a place if its speed increases by 20% when it goes from a place to B and travels 60 kilometers per hour in three hours?

60 × [60 × (1 + 20%)] = 180 × 72 = 2.5 (hours); a: you can return to Jiadi in 2.5 hours

A car from a to B, increase the original speed by 20%, only 6.5 hours to reach B, the original plan to a few hours?
Can the answer be simpler?

Let v be the original velocity and s be the distance between the two places,
When the speed is increased, S / (1.2V) = 6.5
The time before acceleration is s / v = 6.5 * 1.2 = 7.8,
So the original plan is 7.8 hours