Given:
Reduction in the speed of the flight = 20%
Increase in the time of the flight = 2hrs.
Concept:
Using the ratio of speed which is inversely proportional to time.
Formula used:
Speed =
(when distance is same)
Calculation:
Let the usual speed of the flight be x
Speed of the flight during rainfall = 80% of its usual speed =
Rainfall condition : usual condition
We know that when distance is same then the speed is inversely proportional to time
Ratio of two speeds =
: x
⇒ Ratio of time = x :
According to the question,
Increase in the time of the flight = 2 hrs
⇒ x –
= 2
⇒
= 2
⇒ x = 10 hrs
So, usual time of the flight =
=
= 8 hrs
∴ Required answer is 8 hrs