1st Grade Adding and Subtracting Tens Within 100 Lesson (Free PDF)
This adding tens lesson for 1st Grade covers adding and subtracting tens within 100 (Common Core 1.NBT.C.4, 1.NBT.C.5, 1.NBT.C.6), with a free PDF to print.
To add to a two-digit number, add ones to ones and tens to tens. For 34 + 5, the tens stay 3 and 4 + 5 = 9, so the sum is 39. For 10 more or 10 less, change only the tens digit. To subtract tens, count tens: 80 – 30 is 5 tens.
Grade 1 · Common Core State Standards: 1.NBT.C.4, 1.NBT.C.5, 1.NBT.C.6
Key facts in this adding tens lesson
- A two-digit number has tens and ones, like 34 = 3 tens and 4 ones.
- To add ones, keep the tens and add the ones.
- If the ones pass 9, make the next ten first.
- 10 more or 10 less changes only the tens digit.
- To subtract tens, think of tens: 8 tens – 3 tens = 5 tens.
How do you add ones to a two-digit number?
Every two-digit number has tens and ones. To add ones, keep the tens the same and add the ones.
Example: \(34 + 5\). The tens stay at 3. The ones are \(4 + 5 = 9\). So the sum is 39.
What if the ones make a new ten?
Sometimes the ones add up past 9. Then make the next ten first. Split the number you add into two small parts.
- Find how many more make the next ten.
- Add that part first.
- Add the part that is left.
Example: \(38 + 5\). First \(38 + 2 = 40\). Then \(40 + 3 = 43\). So \(38 + 5 = 43\).
How do you add tens to a number?
Add the tens and keep the ones. In \(42 + 30\) the 2 ones stay the same. Think 4 tens and 3 tens make 7 tens. So the sum is 72. On a hundred chart, each jump down one row adds 10.
How do you find 10 more or 10 less?
10 more changes the tens digit and keeps the ones digit. 10 more than 47 is 57. 10 less than 47 is 37. You can do this in your head.
How do you subtract tens?
Count tens, not ones. For \(80 – 30\), think 8 tens minus 3 tens is 5 tens. That is 50. This works for numbers from 10 to 90.
Adding tens lesson: questions and answers
How do you add a one-digit number to a two-digit number?
Keep the tens the same and add the ones. For 52 + 6, the ones are 2 + 6 = 8, so the sum is 58. If the ones pass 9, make the next ten first.
How do you add tens to a number?
Add the tens digits and keep the ones. For 26 + 30, 2 tens plus 3 tens is 5 tens, so the sum is 56. The ones stay 6.
What is 10 more than a number?
It is the number with the tens digit one bigger. 10 more than 63 is 73. On a hundred chart, move down one row.
How do you subtract tens like 70 – 20?
Think of tens. 7 tens minus 2 tens is 5 tens. So 70 – 20 = 50. Check with blocks by crossing out 2 rods.
Can you add numbers in any order?
Yes. 4 + 52 and 52 + 4 both equal 56. Start with the bigger number to make counting easier.
How to use this adding tens lesson
Read the definitions first, then follow the worked method line by line and redo the example on paper without looking. When every step makes sense, move on to the worksheet, then check yourself with the quiz.
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All Grade 1 chapters: Grade 1 math.
