I 64 men do a job in 15 days how many more men are needed to do the job in 12 dsys?

4/5 as many days, 5/4 as many men: 80

So, 16 more men

To find out how many more men are needed to do the job in 12 days, we need to use the concept of man-days, which is the product of the number of men and the number of days required to complete the job.

First, we calculate the man-days to complete the job in 15 days:
Man-days = Number of men * Number of days
Man-days = 64 men * 15 days
Man-days = 960

To find out how many more men are needed to do the job in 12 days, we divide the total man-days required by the number of days:
Number of men = Man-days / Number of days
Number of men = 960 / 12
Number of men = 80

So, 80 more men are needed to complete the job in 12 days.