Is the number 100 a round number?

Responding to Thanh Nien Newspaper reporter, Ms. Trinh Thi Nghia Thao, math teacher at Asia International School, Ho Chi Minh City, said that among the given numbers 1, 10, 100 and 90, the largest round tens answer is 100. This teacher said that in the current first grade math program (General Education Program 2018), students have learned about numbers up to 100; knowledge about tens - round tens.

Accordingly, in the current first grade math textbook, first graders are taught that 1 tens equals 10 units; 2 tens equals 20 units; and so on, 9 tens equals 90 units and 10 tens equals 100 units. Thus, if among the given numbers: 1, 10, 100 and 90, the largest round tens is 100.

The controversial "round tens" problem

However, below the article "Which is the largest round tens number among the numbers 1, 10, 100 and 90?" above, many readers still sent in their opinions. Some readers said: "If you call a round tens number, it only has 2 digits. 3 digits is already hundreds. Since it is a natural number, you should not swap concepts"; "When I was in my 80s, 10, 20,..., 90 were round tens, and 100 was a round hundreds number. So the number 100 cannot be called a round tens number".

A teacher wondered: "If so, can we call 100 a ten tens? I am a former teacher and I am also very confused about the teacher's explanation of grading papers". "So can we call 150 a number of 15 tens or can the number 1,000 be called a number of 100 tens?"...

Thanh Nien Newspaper reporter raised the above questions with Dr. Tran Nam Dung, Vice Principal of the Gifted High School (Ho Chi Minh City National University), expert in creating the STEAM program for this school, and editor-in-chief of the math subject of the Creative Horizon book series. Dr. Tran Nam Dung, a mathematician, said: "The number 100 can be called 10 tens, the number 150 can be called 15 tens. In general, a round number is a positive integer ending in 0. Even 1,000 is a round number. The number 100 is both a round number of hundreds and a round number of tens."

Also according to mathematics doctor Tran Nam Dung, in current textbooks there are exercises listing round tens from 100 to 200.

Regarding how to read numbers, Dr. Dung gave an example that the number 1,230 must be read as "one thousand two hundred thirty" and cannot be read as "one hundred two thirty", but can be read as "123 tens".

The current math textbook for grade 1, Creative Horizon series (Vietnam Education Publishing House) with the lesson on tens, rounded tens, the page clearly states that 10 tens = 100

Source: https://thanhnien.vn/so-100-co-phai-so-tron-chuc-khong-185240910184722546.htm