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Printjmc
number theory junior
Problem
There are 24 four-digit whole numbers that use each of the four digits 2, 4, 5 and 7 exactly once. Only one of these four-digit numbers is a multiple of another one. Which of the following is it?
(A)
(B)
(C)
(D)
Solution
There are only 5 options for the problem so we can just try them. It is easy since that we only need try to use , to divide them. Even will leads to a solution start with which we don't need. , . . , . . The answer is . You can obtain the answer in only 6 calculations.
Final answer
D