seegongsik
Grade 2 (age 7-8)

grade 2 Addition & Subtraction with Carrying

When you add or subtract two-digit numbers, a single column sometimes holds too much or too little. If the ones reach ten, you carry one over to the tens; if the ones are too small to subtract, you borrow ten from the tens. Packing apples ten to a basket is a quick way to feel why that promise is needed. Slide the two numbers and watch, column by column, how carrying and borrowing play out in a vertical sum.

Why do we need to carry?

🧺 Packing apples into baskets
①Each basket holds up to 10 apples
②7 apples and 6 apples make 13, which is too many for one basket
③Move 10 into a new basket and keep the other 3
④Moving a group of 10 up to the next place is called carrying

Addition with carrying

47
36
💡 Steps for carrying
①Add the ones first
②If the sum is 10 or more, write only what is left in the ones place and carry 1 to the tens place
③In the picture, the carried 1 is written in red above the tens
④When you add the tens, add the carried 1 as well

Subtraction with borrowing

63
28
💡 Steps for borrowing
①If you can't subtract the ones digits, borrow 10 from the tens
②In the picture, the tens digit reduced by 1 and the ones digit with 10 added are written in red above
③Subtract in the ones place first, using the borrowed 10
④Then subtract the tens from the reduced tens digit
⑤If the number to take away is set larger, the picture swaps the two so the smaller number is taken from the larger one

Wrap-up

Addition with carrying
47 + 36 → ones: 7+6=13 (write 3, carry 1) → 83
If the sum is 10 or more, carry 10 to the next place
Subtraction with borrowing
63 − 28 → ones: 3<8 → 13−8=5, tens: 5−2=3 → 35
If you can't subtract the ones, borrow 10 from the next place
🎯 Remember
①Always start with the ones
②Carrying: if the ones add up to more than 10, carry 1
③Borrowing: if there aren't enough ones, borrow 10 from the next place
④Writing the carried or borrowed number small helps avoid mistakes
⑤Check a subtraction with answer + number taken away = starting number

Examples and unit check

Example 1
Work out 58 + 27 in columns.
1
Ones: 8 + 7 = 15. Write 5 and carry 1 to the tens.
2
Tens: 5 + 2 + 1 (carried) = 8. So 58 + 27 = 85.
▸ 85
If the ones add up to more than 10, carry 1 to the tens.
Example 2
Work out 72 − 35 in columns.
1
Ones: you can't take 5 from 2. Borrow 10 from the tens: 12 − 5 = 7.
2
Tens: after lending 10, 7 − 1 = 6, and 6 − 3 = 3. So 72 − 35 = 37.
▸ 37
If you can't subtract the ones, borrow 10 from the tens. Check: 37 + 35 = 72.
Unit check
Which is the value of 46 + 38?
①74
②84
③714
④88
▸ ② 84
1
Ones: 6 + 8 = 14. Write 4 and carry 1.
2
Tens: 4 + 3 + 1 = 8. So 46 + 38 = 84.
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Four-digit Numbers
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Multiplication Basics

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