Number Theory Questions and Solutions


Question:
How many numbers with distinct digits are possible product of whose digits is 28?
A.  6
B.  4
C.  8
D.  12
Correct Answer: (C)

 

 

Explanation:
Two digit numbers; The two digits can be 4 and 7: Two possibilities 47 and 74
Three-digit numbers: The three digits can be 1, 4 and 7: 3! Or 6 possibilities.
We cannot have three digits as (2, 2, 7) as the digits have to be distinct.
We cannot have numbers with 4 digits or more without repeating the digits.
So, there are totally 8 numbers.
Answer Choice (C)
Difficulty Level 2

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