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Buy It? Or Don't?

『行事局、数字に、聞いてみた。』英語版 The Decision Deck 第7章「Buy It? Or Don't?」からの実抜粋です。

With the signage and wait-time fixes moving forward, one more decision landed on the table: whether to rent an extra large tent for the food-stall area at the fall festival.

"The extra tent's $300," Miyamoto said, holding up a quote.

"That's a lot. But if it rains, the outdoor stalls lose sales, right?" Minami asked.

"Same thing as the sports festival," Yamato said. "Rain keeps people away from outdoor stalls."

"Then we should get it."

"Or — if it stays dry, that's $300 wasted."

Miyamoto and Yamato landed on opposite sides. Minami looked back and forth between them.

"Sensei — which one's right?"

"Before you ask me — did you compare th—"

Minami caught herself and said it before Nishino-sensei could. He tapped his calculator, and shook his head anyway.

"Before we get to right or wrong, let's lay out the situation first. What happens after you pick 'buy' — and what happens after you pick 'don't buy.' Drawing it out as a tree makes it a lot clearer."

He sketched squares and circles on the whiteboard as he explained. "Squares are choices you control. Circles are chance — weather, in this case, which nobody controls."

"First — 'buy.' Costs $300 up front. But stall revenue holds steady at $1,000 no matter what the weather does."

"And 'don't buy'?"

"No upfront cost," Yamato continued. "But now there's a chance branch. If it's sunny, revenue's $1,000. If it rains, sales drop — call it $400."

"Rain chance for the fall festival, based on the records, is usually around 30%," Miyamoto added.

The four of them studied the finished tree together.

"Buy it, and no matter the weather, you walk away with $1,000 minus $300 — a guaranteed $700."

"Don't buy it, and it's $1,000 if it's sunny... but only $400 if it rains."

Minami crossed her arms. "Hmm. If sunny's more likely, maybe not buying is the smarter move. But if it rains... buying feels a lot safer."

"Good instinct," Nishino-sensei said. "Just drawing the tree doesn't tell you which one to pick yet. To really compare sunny and rainy fairly — accounting for how likely each one actually is — you need one more step."

"How do we do that?"

"That's next time." Nishino-sensei smiled, clearly enjoying holding the answer back a little longer.

Yamato started the sixth card.

[Card #6 — The Fork-in-the-Road Tree] In a word: Draw out the choices you control (squares) and the chance events you don't (circles), branch by branch, to see the whole shape of a decision at once. When to use it: Whenever what happens next depends on which option you pick. Drawing it out on paper catches things your head alone might miss.

"Just drawing it out already made my head feel clearer," Minami said.

Miyamoto nodded. "Seeing 'buy' and 'don't buy' branch off into completely different outcomes, on paper — that hit different than just arguing about it out loud."

478 words

Vocabulary Check

  1. "Costs $300 up front" means the $300 is paid —

    1. after the festival ends
    2. in advance, before the outcome is known
    3. only if it rains
    4. by the customers
    答えを見る

    正解：B．in advance, before the outcome is known

  2. "...holding up a quote" — here, "quote" refers to —

    1. a famous saying
    2. a stated price for a product or service
    3. a direct quotation from a book
    4. a school grade
    答えを見る

    正解：B．a stated price for a product or service

  3. "...you walk away with $1,000 minus $300" means you —

    1. physically leave the room with cash
    2. end up with, as a net result
    3. borrow that amount
    4. donate that amount
    答えを見る

    正解：B．end up with, as a net result

  4. "...accounting for how likely each one actually is" — here, "accounting for" is closest to —

    1. ignoring
    2. taking into consideration
    3. calculating in a bank account
    4. arguing against
    答えを見る

    正解：B．taking into consideration

  5. "Good instinct," Nishino-sensei said — here, "instinct" refers to —

    1. a written report
    2. a natural, immediate sense or judgment
    3. a mathematical formula
    4. a rule memorized in advance
    答えを見る

    正解：B．a natural, immediate sense or judgment

  6. "Miyamoto and Yamato landed on opposite sides" means they —

    1. sat in different chairs
    2. ended up disagreeing with each other
    3. agreed completely
    4. left the room
    答えを見る

    正解：B．ended up disagreeing with each other

  7. "...let's lay out the situation first" means to —

    1. physically place objects on a table
    2. present or explain something clearly and fully
    3. postpone a decision indefinitely
    4. criticize someone's idea
    答えを見る

    正解：B．present or explain something clearly and fully

Comprehension

  1. Why does Nishino-sensei suggest drawing a "tree" instead of simply answering "who's right"?

    1. Because he does not know the answer himself.
    2. Because laying out what happens after each choice makes the situation clearer before judging who is right.
    3. Because trees are required by school rules.
    4. Because Miyamoto asked him to draw something.
    答えを見る

    正解：B．Because laying out what happens after each choice makes the situation clearer before judging who is right.

    「right or wrongの前に、まず状況を整理しよう」という発言の通り、結論を急ぐ前に選択肢と結果を可視化することが目的。

  2. According to the passage, what is the difference between a square and a circle in the tree?

    1. Squares represent money; circles represent time.
    2. Squares are choices you control; circles are chance events you do not control.
    3. Squares are for "buy"; circles are for "don't buy."
    4. There is no real difference.
    答えを見る

    正解：B．Squares are choices you control; circles are chance events you do not control.

    "Squares are choices you control. Circles are chance..."という説明がそのまま定義。

  3. What is the guaranteed outcome if the committee buys the tent?

    1. A guaranteed $1,000, regardless of weather.
    2. A guaranteed $700, regardless of weather.
    3. A guaranteed $400 if it rains.
    4. No guaranteed outcome at all.
    答えを見る

    正解：B．A guaranteed $700, regardless of weather.

    "you walk away with $1,000 minus $300 — a guaranteed $700"の通り、天気に関係なく$700が確定する。

  4. What does Nishino-sensei say is still missing, even after the tree is fully drawn?

    1. The exact chance of rain.
    2. A way to fairly compare the two branches by weighing each outcome by how likely it actually is.
    3. A bigger whiteboard.
    4. Permission from the school principal.
    答えを見る

    正解：B．A way to fairly compare the two branches by weighing each outcome by how likely it actually is.

    最後のセリフ：木を描いただけではまだ足りず、確率を加味した比較（次回に持ち越し）が必要だと示唆している。

  5. According to Card #6, when should the Fork-in-the-Road Tree be used?

    1. Only when a decision involves exactly $300.
    2. Whenever what happens next depends on which option is chosen, since drawing it out can catch things you would miss just thinking it through.
    3. Only after a teacher gives permission.
    4. Only for decisions about weather.
    答えを見る

    正解：B．Whenever what happens next depends on which option is chosen, since drawing it out can catch things you would miss just thinking it through.

    追加した"Card #6"の定義部分（"When to use it"）をそのまま問う設問。頭の中だけで考えると見落としがちなことも、紙に描き出すことで拾える、という説明。

Summary Writing

Summarize the passage in 90–110 words.

モデル要約と解説を見る

A school committee debates whether to spend $300 on an extra festival tent: one member fears losing sales to rain, another worries about wasting money if it stays dry. Rather than declare a winner, their advisor has them draw a decision tree, separating choices they control from chance events like weather. Buying guarantees $700 profit regardless of weather; not buying nets $1,000 if sunny but only $400 if it rains. Seeing the branches laid out clarifies the trade-off, but the advisor notes that comparing the two options fairly still requires one further step: weighing each outcome by how likely it actually is.

102 words

なぜこの要約になるか

  • これも物語（会話文）からの実抜粋。数字を含む具体的なやりとり（$300、$1,000、$400、30%）を、要約では「$700の利益が確定」「晴れなら$1,000・雨なら$400」という結果の数字だけに絞って残している。会話のやりとり自体（誰が何と言ったか）は要約に含めない。
  • 意思決定木という道具の名前（Fork-in-the-Road Tree）よりも、「四角＝コントロールできる選択」「丸＝コントロールできない偶然」という仕組みの説明を優先して残す判断をしている。
  • 102語という制限の中で、最後の「まだ足りない一歩がある」という先生の指摘は、この場面が未解決のまま終わるという物語の構造そのものなので、あえて要約の結びに残している。
  • 後半で追加した"Card #6"の定義（一言でいうと／使いどころ）は、既刊の各章末に登場する定型フォーマットです。要約には固有名詞（Card #6／Fork-in-the-Road Tree）を残さず、「四角＝コントロールできる選択、丸＝コントロールできない偶然」という中身だけを抽出している。

Your Turn

The committee in the passage still had not decided whether to buy the tent by the end of the scene. Based on the decision tree described, what additional information would you want before making a final choice? Write your opinion in English, using 150–190 words.

本文の数字（$300・$1,000・$400・30%）を踏まえて、次に何を確認すべきかを具体的に述べる。「もし〜なら」という条件分岐を使うと1級レベルの構成になる。

使える型

  • Before deciding, I would want to know...
  • This matters because...
  • If ..., then I would choose...
  • Overall, I believe...

考えの道具箱

この英文は、既刊『行事局、数字に、聞いてみた。』英語版 The Decision Deck 第7章「買う？　買わない？」からの実際の抜粋です。「わかれ道の樹」——これから起こりうる分かれ道と、その先の結果を、四角（自分で決めるところ）と丸（運まかせなところ）を使って描き出す——という道具が、そのまま英語のセリフとして登場します。

数字を含む英文を要約するときは、会話のやりとりそのものではなく、「結局いくらになるのか」という結果の数字を優先して拾ってください。ここで拾った$700・$1,000・$400という数字が、要約の骨格になっています。

「わかれ道の樹」のページを見る →

Read the Original

The Decision Deck cover

この考え方が生まれた物語を、英語のまま読む。

The Decision Deck

Did you compare the numbers?

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