別提新加坡了。

The latest brain-mangling maths puzzle to hit the news is from Vietnam。

最近登上新聞頭條的燒腦數學題來自越南。

It’s posted above. You need to fill in the gaps with the digits from 1 to 9 so that the equation makes sense, following the order of operations - multiply first, then division, addition and subtraction last。

如上圖所示。你需要用1到9的數字將所有空格填滿，並且使等式成立，計算的順序為，先乘，接着除，然後是加，最後是減。

According to the VN Express, it was set as a problem for third graders in the town of Bao Loc in the Vietnamese highlands。

據報道，這道題目是越南保祿地區小學三年級的數學題。

That’s eight year olds!

他們可只有8歲啊！

There is no complicated maths involved, only basic arithmetic. But it’s not a walk in the park。

這題目沒有涉及任何複雜的運算，只有基本的算術。但做起來一點也不容易。

“This problem is difficult even for adults good at math, so it will be difficult for students in grades 3, and even more challenging for students in the highlands,” teacher Tran Phuong told VN Express。

一位老師說：“就算對數學很好的成年人來說，這道題也很難解。所以對三年級的學生來說肯定很難，對高地地區的學生就更難了。”

He added: “I sent the problem for some people, including a doctorate in economics with mathematics, but they have not given the answer。”

他還說：“我把這道題發給了一些人，其中包括一位有數學背景的經濟學博士，但他們都還沒有給出答案。”

Vietnam does very well in the international PISA tables that compare 15-year-olds’ performance in maths, science and reading. Vietnam ranks 17 in maths and 8 in science, which outperforms many Western countries like the UK (26 and 20) and US (36 and 28)。

越南的學生在國際學生評估項目的數學、科學和閱讀領域表現都不俗。他們在數學領域排名17，在科學領域排名第8，比英國(這兩項分別排名26和20)和美國(分別排名36和28)都出色。

No wonder if they are given problems like this..。.

難怪他們能出這樣的題目....。.

Can you do it?

你能解出這道題嗎？

Here is one of the solutions from a commenter at Gizmodo: There are other possible solutions, but the first one I came up with was: 6, 9, 3, 5, 2, 1, 7, 8, 4 in that order ... How I got to it was assigning each blank to a letter and writing the whole thing as an equation then grouping like terms。

以下是Gizmodo網站一位網友給出的答案：可能還有別的解法，但我最先想到的是：空格中依次填6, 9, 3, 5, 2, 1, 7, 8, 4。我用字母代替每一個空格，然後把整個等式列出來，再進行同類項合併。

So... a+13(b/c)+d+12e-f+(gh/i)-21=66.

算式是這樣的：a+13(b/c)+d+12e-f+(gh/i)-21=66。

Then you add 21 to both sides and a+d-f+13(b/c)+12e+(gh/i)=87. And since you’re limited to plugging in numbers between 1-9 for a-i, you see that there’s only so many combinations that will yield numbers close to 87. So then you start guessing and checking how large you have to make the various numbers to make it work. You need smaller numbers in the denominators and the subtraction and larger numbers being multiplied。

給算式兩邊都加21，就得出a+d-f+13(b/c)+12e+(gh/i)=87。字母a到i的空格中只能填入1到9 的數字，計算結果能得出87的變化組合也就那麼多。所以你就可以邊猜邊調整，最後得出正好的結果。分母和減號後面的數字要小一些，乘號後面的數字要大一 些。

Vocabulary:

brain-mangling: 費腦筋的，燒腦的

walk in the park: 很容易的事

like terms: 同類項

denominator: 分母