2021 AMC 10A Problem 7
Problem 7 of 25Easier
Tom has a collection of snakes, of which are purple and of which are happy. He observes that
• all of his happy snakes can add,
• none of his purple snakes can subtract, and
• all of his snakes that can’t subtract also can’t add.
Which of these conclusions can be drawn about Tom’s snakes?
Answer choices
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Solution
Note that the third condition ensures that purple snakes can’t add.
We also know that all happy snakes can add, which means that happy snakes can’t be purple as well.
Thus, D is the correct answer.