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Related facts이어지는 계산식

If 3 + 4 = 7, then 30 + 40 = 70.

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한국어 요약

3 + 4 = 7을 알면 30 + 40 = 70도 풀 수 있다는 것을 영어로 가르치는 법이에요. 20 + 50 = 700 같은 실수를 tens라는 말로 바로잡고, thirteen과 thirty처럼 헷갈리는 발음도 함께 연습해요.

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The big idea핵심

Lia can use a small fact to find a big fact. 3 ones + 4 ones = 7 ones, so 3 tens + 4 tens = 7 tens. 7 tens is 70. So 30 + 40 = 70. We are counting tens in the same way we count ones or apples. A common mistake is 20 + 50 = 700. Talking about “tens” stops this mistake.

+
3 ones + 4 ones = 7 ones
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3 tens + 4 tens = 7 tens = 70

Get ready준비물

  • Lego towers of 10 (or bundles of 10 straws or ice-cream sticks)
  • Some single bricks
  • Coins: 10 sen coins are perfect. Each one is a ten.

Teach it, step by step단계별 수업

YOU 부모가 할 말LIA 아이가 할 만한 대답DO 손으로 할 일

Things, not only numbers

YOU“3 apples and 4 apples make…?”
LIA7 apples.
YOU“3 cars and 4 cars make…?”
LIA7 cars.
YOU“3 tens and 4 tens make…?”
LIA7 tens!
YOU“Yes! It works for apples, cars and tens.”

Show with tens

DOGive 3 towers of 10.
YOU“Each tower is 1 ten. How many tens are here?”
LIA3 tens.
YOU“3 tens is 30. Let's count: 10, 20, 30.”
DOAdd 4 more towers.
YOU“Now how many tens?”
LIA7 tens.
YOU“7 tens is 70. So 30 + 40 = 70.”

Use money

DOShow three 10 sen coins and four 10 sen coins.
YOU“How much money is this?”
LIA70 sen.
YOU“3 coins and 4 coins make 7 coins. Each coin is 10 sen. So 30 sen + 40 sen = 70 sen.”

Taking away tens

YOU“8 − 3 = 5. So 80 − 30 = …?”
LIA50.
YOU“How do you know?”
LIA8 tens take away 3 tens is 5 tens. 5 tens is 50.

Spot the mistake

YOU“Amir says 20 + 50 = 700. Is he right?”
LIANo!
YOU“Why not?”
LIA2 tens and 5 tens make 7 tens. 7 tens is 70, not 700.
광고

Say the numbers clearly

Tens numbers and teen numbers sound similar. Say them slowly, and practise with Lia:

Teen numberTens numberHow to hear the difference
13 thirTEEN30 THIRtyTeen numbers are strong at the end. Tens numbers are strong at the start.
14 fourTEEN40 FORtySpelling: forty has no u (not fourty).
15 fifTEEN50 FIFty
16 sixTEEN60 SIXty
17 sevenTEEN70 SEVenty
18 eighTEEN80 EIGHty
19 nineTEEN90 NINEty
  • 13 thirTEENTens number30 THIRtyHow to hear the differenceTeen numbers are strong at the end. Tens numbers are strong at the start.
  • 14 fourTEENTens number40 FORtyHow to hear the differenceSpelling: forty has no u (not fourty).
  • 15 fifTEENTens number50 FIFtyHow to hear the difference
  • 16 sixTEENTens number60 SIXtyHow to hear the difference
  • 17 sevenTEENTens number70 SEVentyHow to hear the difference
  • 18 eighTEENTens number80 EIGHtyHow to hear the difference
  • 19 nineTEENTens number90 NINEtyHow to hear the difference

Other ways to say it다른 표현

  • “3 tens add 4 tens”
  • “thirty plus forty”
  • “What is 30 more than 40?”
  • “What is 40 add 30?”
  • “How many tens is 70?”
  • “What is 20 less than 90?”
  • “Use 5 − 2 to help you find 50 − 20.”

Good questions to ask좋은 질문

  • “Which small fact helps you?”

    Note

    For 60 + 30, the small fact is 6 + 3.

  • “How many tens is 90?”

  • “Why is 20 + 50 not 700?”

    Note

    Reasoning question. Use the word tens in the answer.

  • “What do you notice? 100 − 10, 100 − 20, 100 − 30…”

    Note

    The answers go down in tens: 90, 80, 70.

If Lia is stuck막힐 때

  • When

    She writes 20 + 50 = 7.

    “7 what? 7 ones or 7 tens?” Show 7 towers.

  • When

    She writes 700.

    Build it with towers. “Count the tens with me: 10, 20, 30, … 70.”

  • When

    She confuses 17 and 70 when you speak.

    Say the number, then write it. Use the table above.

Game놀이

Game · Tens shop

You need: 10 sen coins (or paper coins) and some toys with price tags: 20 sen, 30 sen, 50 sen…

  1. Lia is the shopkeeper. You buy two toys: “I want the 30 sen car and the 40 sen ball. How much is that altogether?”
  2. Lia uses the small fact: 3 + 4 = 7, so 70 sen.
  3. Give her 90 sen: “How much change?” (90 − 70 = 20). Swap roles.

Extra challenge더 도전

  • Hundreds: 300 + 400 = 700. “3 hundreds and 4 hundreds make 7 hundreds.”
  • Missing number: 60 + ? = 90.
  • Three tens numbers: 20 + 30 + 40 = ?
In the workbook

Use a small fact, base 10 pictures, the ‘700’ mistake, and a pattern.

워크북 9쪽 보기이 주제 인쇄

자주 묻는 질문

30 + 40은 왜 70인가요?

3 tens와 4 tens를 더하면 7 tens, 곧 70이에요.

thirteen과 thirty는 어떻게 구별하나요?

thir-TEEN은 끝을, THIR-ty는 앞을 세게 말해요. 지도서의 발음 부분에서 함께 연습해요.

광고