Famous as an intellectual program for the top excellent students in the country, Road to Olympia always has a treasure of extremely diverse and complete questions in all fields. The questions are interwoven and gradually increase in level in each part of the contest, so every time the program is broadcast, it receives a lot of attention from the audience.

It was thrilling due to witnessing the competition of excellent students, but in the program there were still many questions that were considered quite easy, and many viewers were excited to answer them in a short time. Especially for Math questions, both interesting but also stimulate quick “jumping numbers”. A question in the program Road to Mount Olympia 17, February, and Quarter III made many people interested, the content is as follows:

From the digits 1, 2, 3, how many 3-digit numbers can be formed that are divisible by 3?

Source: Road to Mount Olympia

After watching the program, many people commented that this is a pretty easy question because just knowing the rule of numbers being divisible by 3 can quickly find the answer. However, the candidate has not yet scored on this question.

Then, there is a contestant who rings the bell to win the right to answer and gives the correct answer of 9 numbers.

To solve this question, we just need to apply the rule: Numbers whose sum of digits is divisible by 3 are divisible by 3 and only those numbers are divisible by 3. In which, the sum of 3 numbers 1, 2 , 3 is 6 divisible by 3, so just form three digit numbers from these 3 numbers to find the answer. The numbers created from the number 1, 2, 3 that are divisible by 3 are: 111, 222, 333, 123, 132, 213, 231, 312, 313.

How long did it take you to find the answer to this question?