Grade 3Math
Division, Subtraction, and MultiplicationHow many times you can subtract, and where the □ goes
You can also find the answer to 12 ÷ 3 by finding how many times you can subtract 3 from 12. If you think with a multiplication math sentence that uses □, you can also see that the □ goes in a different place depending on whether you find the number of groups or the number in one group.
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
- 3 problems
Open this lesson in Japanese（わり算と ひき算・かけ算）
Let's try
Write the math sentence in your notebook first, then open the answer.
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1Find the answer to 15 ÷ 5 by subtracting again and again.
Hint
Keep subtracting 5 from 15, and count how many times you could subtract until you reach 0.
Answer
It is 3. 15 − 5 = 10, 10 − 5 = 5, 5 − 5 = 0. You subtract 5, and after 3 times you get 0, so 15 ÷ 5 = 3.
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2There are 20 cards. If 4 people share them equally, how many cards does each person get? Make one person's share a □, write a multiplication math sentence, and find the □.
Hint
One person's share × the number of people = the total. You don't know one person's share, so the first number in the multiplication is the □.
Answer
The math sentence is □ × 4 = 20. 5 × 4 = 20, so the □ is 5. Each person gets 5 cards (20 ÷ 4 = 5).
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3There are 18 candies. If you put 3 candies in each bag, how many bags can you make? Make the number of bags a □, write a multiplication math sentence, and also say which times table you use to find it.
Hint
The number in one bag × the number of bags = the total. You don't know the number of bags, so the second number in the multiplication is the □.
Answer
The math sentence is 3 × □ = 18. If you look in the 3 times table, 3 × 6 = 18, so the □ is 6. You can make 6 bags (18 ÷ 3 = 6).
Words in this lesson
- subtracting again and again くり返し ひく
- Subtracting the same number many times. If you subtract 3 from 12 four times, you get 0.
- number of groups いくつ分
- How many groups of the same number there are, such as the number of times you took 3.
- one group 1つ分
- The number for one person or one plate when you share equally.
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).
- Division can also be thought of as subtracting the same number again and again and counting how many times you can subtract (12 − 3 − 3 − 3 − 3 = 0, and there are 4 threes, so 12 ÷ 3 = 4). Try actually removing marbles or candies 3 at a time and counting the number of times.
- When written as a multiplication math sentence, finding the number of groups is 3 × □ = 12, and finding the number in one group is □ × 3 = 12, so the □ is in a different place. If you hand out one to each person, 3 are gone each round, so in both cases the answer can be found with the 3 times table.