Answer:
His new time is twice his old time :

Explanation:
- We need to use an equation that relates speed, distance and time. We are going to use the following equation :

Where ''v'' is the speed
Where ''d'' is the distance
And where ''t'' is the time
- We know by reading the exercise that :
(I)
Where ''
'' is the speed of the first trip and where ''
'' is the time of the first trip.
- The equation of the second trip is :
(II)
Where ''
'' is the time of the second trip.
- If we use (I) in the equation (II) :
⇒




We find that the time of his second trip is twice as the first one.