Answer: The required number of cans is 7.42.
Step-by-step explanation: Given that last month, Hao dog ate 40 cans of dog food in 31 days.
We are to find the number of cans that he should buy to feed his dog for the next 6 days.
We will be using the UNITARY method to solve the given problem.
Number of cans required to feed the dog for 31 days = 40.
So, the number of cans that is required to feed the dog for 1 day is

Therefore, the number of cans that is required to feed the dog for 6 days is given by

Thus, the required number of cans is 7.42.