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counting and probability senior

Problem

How many even three-digit integers have the property that their digits, all read from left to right, are in strictly increasing order?
(A)
(B)
(C)
(D)
Solution
Let the integer have digits , , and , read left to right. Because , none of the digits can be zero and cannot be 2. If , then and must each be chosen from the digits 1, 2, and 3. Therefore there are choices for and , and for each choice there is one acceptable order. Similarly, for and there are, respectively, and choices for and . Thus there are altogether such integers.
Final answer
B