Thomas is making hummus. One of the ingredients in a hummus recipe is chickpeas. For one serving of hummus, the recipe calls for 1 cup of chickpeas. In a can of chickpeas, there are 16 ounces of chickpeas. In one cup of chickpeas, there are 6 ounces. To make 20 servings, how many cans of chickpeas should Thomas buy?
Please reason step by step, and put your final answer within \boxed{}.
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