Thanks for the explanation. now i see it. i confused because of this fragment "about 22,000km to recover".
Your calculation is the way that hybrid users do math.if i use your figures to formulate this (even though non of them are realistic ):
to recover 290,000 rupees from X number of kilometers,
X/15 - X/25 = 290,000/130, find X
it is 84000 Km,
if you had to travel 84000 km using a 15kmpl car, then cost is 728000/=
If it is a car with 25kmpl , then cost is 436800/=
then you have saved = aporx 290,000/=
I think now you can see why i was unable to figure out your calculation.