Jon's laundry machine can do 5 pounds of laundry at a time. 4 shirts weigh 1 pound and 2 pairs of pants weigh 1 pound. If he needs to wash 20 shirts and 20 pants, how many loads of laundry does he have to do? Let's think first. Chain of thought:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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The shirts weigh 20 / 4 = 5 pounds. The pants weigh 20 / 2 = 10 pounds. So he needs to do 10 + 5 = 15 pounds of laundry. So that would take 15 / 5 = 3 loads of laundry.
Therefore, the answer is 3.