Question 72452
On 14th Jan, 8 am the size of the creature was 100 cu ft.
It doubles its size in each day.
It dies on 19th (8 am, assumed).
So we have to find how much its size increased in 5 days.
On 15th its size = 200 cu ft.
On 16th its size = 400 cu ft.
On 17th its size = 800 cu ft.
On 18th its size = 1600 cu ft.
On 19th its size = 3200 cu ft.


Thus the size of the creature was 3200 cubic feet when it died.


Remark: This problem could also have been solved by G.P. series method.