2. The first two digits of a four-digit number are either each less than 5 or each greater than 5. The same can be said about the last two digits. How many such numbers are there?
Answer: 1476.

## Solution:

If the first 2 digits are less than 5, this gives $4 \cdot 5=20$ options, and if they are greater than 5, it gives $4 \cdot 4=16$ options.

If the last 2 digits are less than 5, this gives $5 \cdot 5=25$ options, and if they are greater than 5, it gives $4 \cdot 4=16$ options.

Total options: $(20+16) \cdot(25+16)=1476$.

## Instructions for Checking:

Answer without justification - 0 points. Penalty for calculation errors - 2-3 points.