Is 100 a multiple of ten?

Responding to a reporter from Thanh Nien Newspaper, Ms. Trinh Thi Nghia Thao, a math teacher at the Asian International School in Ho Chi Minh City, stated that among the numbers given – 1, 10, 100, and 90 – the largest multiple of ten is 100. She explained that in the current first-grade math curriculum (2018 General Education Program), students have already learned about numbers up to 100, including tens and multiples of ten.

Accordingly, in the current first-grade math textbook, first-grade students learn that 1 ten equals 10 units; 2 tens equals 20 units; and so on, 9 tens equals 90 units and 10 tens equals 100 units. Thus, among the given numbers: 1, 10, 100 and 90, the largest multiple of ten is 100.

The "round-ten" problem sparks controversy.

However, below the article "Which is the largest multiple of ten among 1, 10, 100, and 90?" , many readers still sent in their opinions and debates. Some readers said: "If it's called a multiple of ten, it should only have two digits. Three digits would go up to hundreds. Since it's a natural number, we shouldn't confuse the concepts"; "When I was in the 80s, numbers like 10, 20, ..., 90 were multiples of ten, and 100 was a multiple of one hundred. So, 100 cannot be called a multiple of ten."

One teacher wondered, "If so, can we call 100 'tens of tens'? I'm a former teacher and I'm also very confused about how teachers grade explanatory papers." "Then, can we call 150 '15 tens' or 1,000 '100 tens'?"...

A reporter from Thanh Nien newspaper posed these questions to Dr. Tran Nam Dung, Vice Principal of the High School for the Gifted (Vietnam National University, Ho Chi Minh City), a specialist in creating the STEAM program for this school, and the chief editor of the mathematics subject in the "Creative Horizons " textbook series. Dr. Tran Nam Dung stated: "The number 100 can be called ten tens, the number 150 can be called fifteen tens. In general, a round number is a positive integer ending in the digit 0. Even 1,000 is a round number. The number 100 is both a round hundred and a round ten."

According to Dr. Tran Nam Dung, a mathematician, current textbooks include exercises that require listing multiples of ten from 100 to 200.

Regarding how to read numbers, Dr. Dung gave the example that the number 1,230 should be read as "one thousand two hundred thirty" and not "one hundred two thirty," but saying "123 tens" is acceptable.

The current first-grade math textbook, part of the "Creative Horizons" series (Vietnam Education Publishing House), has a lesson on tens and multiples of ten, with the page clearly stating that 10 tens = 100.

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