If it takes 4 people 20 days to build a house, how long does it take 6 people. I know the answer is 15 days, but for the life of me I can't figure out the formula for it.

To determine how long it would take 6 people to build the house, you can use the concept of "person-days." A person-day represents the amount of work one person can complete in one day.

Given that it takes 4 people 20 days to build the house, we can calculate the total person-days required to complete the project. We multiply the number of people by the number of days:

4 people * 20 days = 80 person-days

Now, to find out how many days it would take 6 people to build the house, we divide the total person-days by the number of people:

80 person-days / 6 people = 13.33 days

Therefore, it would take approximately 13.33 days for 6 people to build the house. Since we usually express time in whole numbers, you can round it up to 14 days or down to 13 days, depending on the context.

20 days are required for 4 people to build a house. So it takes 4*20=80 man-days.

If we have 6 people, then it should take 80/6=13.3 days to finish the house.