3. (7 points) The number 20 is written on the board. In one move, it is allowed to either double the number or erase its last digit. Is it possible to get the number 25 in several moves?
Answer. Possible.

Solution. The number 25 can be obtained by erasing the last digit of the number 256, which is a power of two. Thus, the required chain of transformations can look like this:

$$
20 \rightarrow 2 \rightarrow 4 \rightarrow 8 \rightarrow 16 \rightarrow 32 \rightarrow 64 \rightarrow 128 \rightarrow 256 \rightarrow 25
$$

There are other solutions as well.

## Grading Criteria.

- Any complete correct solution -7 points.
- Incomplete solution (for example, it is stated that 25 can be obtained from the number 256, but it is not specified how to get 256) -3 points.
- Only the answer is provided -0 points.