1 · Counting on
To add a small number, start with the big number and count on. 8 + 3: say "8", then count 9, 10, 11.
Three hops from 8 land on 11.
2 · Doubles and near doubles
Doubles are the same number twice: 6 + 6 = 12, 7 + 7 = 14, 8 + 8 = 16. Learn them by heart.
A near double is one more: 6 + 7 is 6 + 6 and one more, so 13.
3 · Making ten
Ten is a friendly number. 8 + 5: move 2 dots into the frame to make 10. Then 3 are left: 10 + 3 = 13.
So 8 + 5 = 8 + 2 + 3 = 13. Fill the ten first, then add what is left.
4 · Fact families
Adding and subtracting are opposites. The numbers 5, 7, and 12 make a fact family: 5 + 7 = 12, 7 + 5 = 12, 12 − 5 = 7, 12 − 7 = 5.
The biggest number goes on top. Know one fact and you know all four.
5 · Adding tens
30 + 40 is just 3 tens + 4 tens = 7 tens = 70. Count the rods.
The same trick works for taking away: 70 − 20 = 5 tens = 50.
6 · Two-digit adding
Line the numbers up: ones under ones, tens under tens. Add the ones first, then the tens.
23 + 45: ones 3 + 5 = 8. Tens 2 + 4 = 6. Answer 68.
7 · Regrouping: when the ones go over 9
37 + 25: ones 7 + 5 = 12. That is 1 ten and 2 ones. Write the 2, carry the 1 ten up to the tens column.
Tens: 1 + 3 + 2 = 6. Answer 62.
8 · Two-digit subtracting
Subtract the ones first, then the tens. 45 − 12: ones 5 − 2 = 3. Tens 4 − 1 = 3. Answer 33.
9 · Regrouping: when you cannot take away
63 − 47: you cannot take 7 from 3. Borrow a ten: the 6 tens become 5 tens, and the 3 ones become 13 ones.
Now 13 − 7 = 6, and 5 − 4 = 1. Answer 16.
10 · Missing numbers
An equation is a balance. 9 + □ = 18: what goes with 9 to make 18? 18 − 9 = 9.
□ − 7 = 5: the number was 5 before 7 was taken away, so add it back: 5 + 7 = 12.
11 · Clue words in stories
"Altogether" and "in all" mean add: Omar has 22 books and Tom has 34. Altogether: 22 + 34 = 56.
"Left", "how many more", and "fewer" mean subtract: Sam had 44 grapes and gave away 31. Left: 44 − 31 = 13. Ava has 21 shells, Tom has 8. How many more: 21 − 8 = 13.
12 · Three numbers and checking
Adding three numbers? Look for a double or a ten first. 8 + 8 + 9: the double 8 + 8 = 16, then 16 + 9 = 25.
Check a subtraction by adding back: 63 − 47 = 16, because 16 + 47 = 63. You are ready for the test! 🎉
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