There is a 7-digit number X in which all the digits are different. Using the digits of X, two 5-digit
numbers Y and Z are formed, such that no digit is repeated within Y or within Z. What is the
MINIMUM number of digits that Y and Z must have in common?

Answer: C. 3

Number X has 7 unique digits available.
Number Y uses 5 of those digits, leaving 2 unused.
To minimize overlap, Number Z first uses those 2 unused digits.
Since Z must contain 5 digits, it must take its remaining 3 digits from Y.
Therefore, the MINIMUM number of common digits is 3.

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