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エレメンタリーまなびの未来

Grade 3Math

Multiplication in ColumnsCarrying, and how to write with the places shifted

In the column method for multiplying a 2-digit number by a 1-digit number, you calculate with the times tables starting from the ones place, and add the carried number to the tens place.

The narration and the pictures are in Japanese. You can hear the same words that are used in class at a Japanese school.

Video
1:35（7 scenes）
Problems
2 problems

Open this lesson in Japanese（かけ算の 筆算）

0:00
  1. 1Let's use the column method0:00
  2. 2Start from the ones place0:10
  3. 3The tens place0:27
  4. 4The answer0:38
  5. 5Multiplying by a two-digit number0:52
  6. 6Add to get the answer1:12
  7. 7Let's try1:24

Let's try

Write the math sentence in your notebook first, then open the answer.

  1. 1Calculate 26 × 3 with the column method.

    Hint

    Calculate with the times tables from the ones place, and add the number you carried to the tens place.

    Answer

    It is 78. In the ones place, 6 × 3 = 18, so write 8 in the ones place and carry 1 to the tens place. In the tens place, 2 × 3 = 6, and 6 + 1 = 7.

  2. 2In 23 × 14, why do you write the answer to 23 × 1 shifted one place to the left?

    Hint

    The tens digit of the number you multiply by shows how many tens there are.

    Answer

    Because the 1 in the number you multiply by is the 1 in the tens place, so it really means 23 × 10 = 230.

Words in this lesson

column method 筆算ひっさん
A way of calculating where you write the numbers with their places lined up in columns.
carrying くり上がりくりあがり
When the calculation in a place becomes 10 or more, moving the group of 10 to the next place up.

For parents and guardians

  • The names of lessons and the order of topics differ slightly between textbooks. This page follows the content of Japan's national curriculum guidelines (the Course of Study).
  • Writing the carried number small above the tens place helps prevent forgetting to add it. Please check together that the tens digit of an answer from the times tables is the part that gets carried.
  • In the column method for multiplying by a two-digit number, explaining why the answer from multiplying by the tens digit is written shifted one place to the left (because it stands for groups of ten), and connecting it to multiplying by 10, makes it easier to understand.