A total of 15 delegates from Africa, Asia, America, and Europe meet at an international conference.
Each continent sends a different number of delegates, and each is represented by at least 1 delegate.
America and Asia send a total of 6 delegates.
Asia and Europe send a total of 7 delegates.
Which continent has sent 4 delegates?
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How many delegates are from Asia? Since they make a total of 6 with those from America which has sent at least 1, they can be 1, 2, 3, 4, or 5. 3 is impossible since it would yield an equal number of delegates from America. 1 would yield 5 from America, 6 from Europe, and hence 3 from Africa. This is impossible, for one continent has sent 4 delegates. 2 would yield 4 from America, 5 from Europe, and 4 from Africa, which is impossible, for America and Africa would have sent the same number.
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