4. In a drum, there are balls on which all three-digit numbers are written (each one once). One ball is drawn. What is the probability that the sum of the digits of the drawn number is 2 or 5?
First method:
There are 900 three-digit numbers, so there are as many balls in the drum. ..... $1 \text{ POINT}$
The sum of 2 can be obtained by drawing three balls (200, 110, 101). ..... $1 \text{ POINT}$
The sum of 5 can be obtained by drawing 15 balls (500, 410, 401, 320, 302, 311, 230, 203, 221, 212,
140, 104, 131, 113, 122). ..... 2 POINTS
The sum of the digits equal to 2 or 5 can be achieved by drawing one of 18 balls. The probability of this happening is 18 : $900=0.02=2 \%$. ..... 2 POINTS
TOTAL 6 POINTS