The number of 4 digit numbers that can be made using exactly two digits out of 1,2,3,4,5,6 and 7

Options

A. 126
B. 210
C. 284
D. 294

Explanation

To solve the problem of finding the number of 4-digit numbers that can be made using exactly two digits out of the digits 1, 2, 3, 4, 5, 6, and 7, we can follow these steps:

### Step-by-Step Solution:

1. **Choose 2 Digits from 7**:
We need to select 2 digits from the available 7 digits (1, 2, 3, 4, 5, 6, 7). The number of ways to choose 2 digits from 7 is given by the combination formula:
\[
\text{Number of ways} = \binom{7}{2} = \frac{7!}{2!(7-2)!} = \frac{7 \times 6}{2 \times 1} = 21
...