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