Create a table based on the following formulae for the number of each type of fishes:
Number of big fish = Number of big fish at the end of the previous day + 25 — number of big fishes that die each day (Note that the number of big fishes that would die on 10th of August) — when they become 10 days old would be 100, while the number of big fishes that would die subsequently would be 25 every day. Also, since the number of big fishes being added is 25 per day too, from the 11th of August the number of big fishes would be constant. Thus, the pattern for the number of big fishes would be:
1st2nd3rd4th5th6th7th8th9th10th11th12thAugAugAugAugAugAugAugAugAugAugAugAug125150175200225250275300325250250250
Create similar number strings for the other fishes to solve the question.
So on any particular day, the number of medium fishes = number of medium fishes on the previous day +250 - number of big fishes on that day × 1.
Likewise, number of smaller fishes = number of small fishes on the previous day × 2 - number of medium fishes after incrementing the medium fishes for that day × 3.
The answers can be worked out once you form tables for the medium and small fishes too.