kal to bari jaldi aap bata rahe thay 
anyways, there are a lot of methods to calculate.
meri gari me 2 ltr pehle se tha, aur mene nikalte sath hi 1000 rs ka dalwaya.
abhi 220 km chali he, and i think thora sa hi reh gya he tank me.
so, i have a bottle with 1 ltr petrol in it,
so jahan gari ne band hone ki koshish ki, wahan botle se daal dun ga.
but this approach might not be good if done again n again, cz fuel pump empty hoga, jo k acha nahi he,
isliye sirf me ek baar hi kerun ga aesa.