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jmc

number theory junior

Problem

The unit's digit (one's digit) of the product of any six consecutive positive whole numbers is
(A)
(B)
(C)
(D)
Solution
Within six consecutive integers, there must be a number with a factor of and an even integer with a factor of . Multiplied together, these would produce a number that is a multiple of and has a units digit of .
Final answer
A