Have you ever wondered why ❓ it ❓
When I got on the Shinkansen
"Why is it divided into two seats and three seats?"
Have you ever thought ❓
Actually, this is divided into arithmetic and mathematical meanings
All groups of two or more people can sit well.
For example
11 people are 2 × 1 + 3 × 3
17 people are 2 × 4 + 3 × 3
It can be expressed as the sum of multiples of 2 and multiples of 3.
Since all numbers greater than or equal to 2 can be represented in this way,
You can sit well divided into Shinkansen seats ✨
This problem is a frequent problem for both private and public junior high school entrance exams
Let's save this post and remember how to solve it.
Example: How many people can be divided into groups of 4 and 5 ❓
in a problem like this
① Write a table of numbers by arranging numbers for each smaller number of two numbers and breaking lines
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
② If you look at these tables vertically
Since the rightmost column is a multiple of 4, it can be divided into groups of only 4 people. Therefore, all numbers below 4 are erased.
③ The number below 5 is also a number obtained by adding a multiple of 4 to 5, so erase it
④ Similarly, erase the numbers below 10 and below 15
The largest number left is 11.
11 people cannot divide well,
If there are more than 12 people, it can be divided well
And can be solved 💡
Many familiar problems can be solved by arithmetic and mathematics
Please come to like math and math ✨
Problems you do not understand are always in the comments 💬
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Former elementary school teacher 🏫 → Professional tutor ✏️
↓ Have fun learning math Post from here
Tutoring to love learning ✨
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Junior High School Exam # math The study method # parenting # math
検索で多い「新幹線の席って何人席？」「座席数はどうなってる？」を、私が子どもに聞かれて答えた流れで補足します。 まず新幹線の普通車は、1列が「2人席＋3人席」の並び（=合計5席）になっている車両が多いです。だから“1列あたり何席？”と聞かれたら基本は5席、と覚えておくとイメージしやすいです（※路線・車両で違うこともあるので、正確な席数は乗る列車の座席表で確認が安心）。 次に「何人席なの？」という疑問。感覚的には2人席・3人席の2種類ですが、算数的に見るとここが面白いポイントで、人数Nに対して N = 2a + 3b（a,bは0以上の整数） の形で表せれば、その人数のグループが“2人席をa列分、3人席をb列分”使ってきれいに座れます。 実際に小さい数で試すと、1人は2人席や3人席だと必ず1席余るので「ぴったり」にはしにくい。一方で2人=2、3人=3、4人=2+2、5人=2+3、6人=3+3（または2+2+2）…と、2人以上はどんどん作れます。つまり「2人以上のすべての人数のグループが座れる」という説明につながります。 ここから中学受験っぽい実用テクにもつながります。たとえば家族旅行で「7人グループならどう取る？」と考えると、7=2+2+3。つまり“2人席を2列分＋3人席を1列分”でぴったり。9人なら9=3+3+3で3人席だけ、10人なら10=2+2+3+3など、頭の中で分解できると座席数の見通しが良くなります。 最後に、実際の予約では“ぴったりにこだわりすぎない”のもコツです。荷物が多いときは2人席側を多めに取ったり、景色を優先して窓側中心にしたり。算数の「2と3で人数を作れる」視点を持つと、座席選びがちょっと楽しく、迷いにくくなりました。