Answer: 4
Step-by-step explanation:
Given : The number of math problems completed by Fred = 10
The percentage of the the proportion number of math problems he has to do = 40%
The proportion of math problems problems he has to do = 0.40
Then the number of math problems he has to do = [tex]0.40\times10=4[/tex]
Hence, the number of math problems he has to do =4