## Task B-1.1.

Tena thought of a natural number, multiplied it by 17, and wrote the result on the board. Vito erased the last digit, multiplied the resulting number by 8, and wrote the result on the board. Tena erased the last digit of his result, and the number 56 remained on the board. What number did Tena think of?
## Solution.

If the number on the board is 56, it means Vito obtained a number between 560 and 569 by multiplying by 8.

In this interval, there are two numbers divisible by 8: \(560 = 70 \cdot 8, 568 = 71 \cdot 8\). 2 points

By multiplying by 17, Tena obtained a number between 700 and 719. 1 point

In this interval, there is only one number divisible by 17: \(714 = 42 \cdot 17\). 1 point

Tena thought of the number 42.

1 point

Note: If a student omits one of the numbers 560 or 568 from consideration but continues with the correct procedure following this mistake, they receive 5 points.