A garrison of 500 persons had provisions for 27 days. After 3 days a reinforcement of 300 persons arrived. For how many more days will the remaining food last now?

Let the remaining food will last for D days.
500 men had provisions for (27 − 3) = 24 days.
( 500 + 300 ) men had provisions for D days.
More men, Less days ( Indirect Proportion )
we can write as :-
∴ 800 : 500 :: 24 : x ⇔ (800 × D ) =( 500 × 24 )
⇔ ( 500 × 24 ) /800 =15
Therefore , 15 days is correct answer .