Math problem: invisible dice

Math problem: invisible dice

today,
The little granddaughter ask me a math topic.
I was Will not answer.

The little granddaughter said:
There are 3 dice, stacked vertically,
The top face is the number of points 5,
how much are those total points that I can't see's point?

The algorithm is 7*3-5=16

Because the 2 opposite faces of the dice, the total is 7,
For example, the opposite of 6 is 1.
the three dice are stacked vertically, and a total of five faces are invisible.
That is, there are 3 sets of opposite faces.
One of the face is 5 ,
So the algorithm is 7*3-5=16

So this question math problem,
With this 7 common sense, you can answer in seconds.
Without this common sense, you can’t think of an answer.

数学问题:看不见的骰子

今天,
小孙女拿了一道数学题目,
我被问倒了.

小孙女说:
有3个骰子,垂直的叠在一起,
最上面的那一个面是点数5,
请问看不到的那些面,合计点数是多少?

这题目,技巧的,秒答,可我不知道,所已当场呆住.

算法是 7*3-5=16

因为骰子的相对的两个面,合计为7,
比如6的对面就是1,
而3个骰子,垂直的叠在一起,共有5个面是看不到的,
也就是有3组相对的面,
其中有1个面是看的到的,就是题目中的5,
所以算法为7*3-5=16

所以这题数学题,
有这个7的常识,就能秒答.
没有这常识的,怎想,也想不出来答案.