10 More, 10 Less, 100 More & 100 Less | Grade 2 Math

Grade 2 Math  ›  Numbers & Place Value  ›  Lesson 6

Grade 2 Math - Numbers and Place Value

10 More, 10 Less, 100 More & 100 Less

Learn to use place value to mentally find 10 more, 10 less, 100 more, and 100 less than a given number. Students connect each change to tens and hundreds instead of counting one by one.

The lesson includes straightforward place-value changes, important boundary cases such as 295 + 10 = 305, and reasoning with opposite changes so students understand why the method works.

10 more 10 less 100 more 100 less Mental math Place value

🎯 What You Will Learn

Find 10 more or 10 less
Think about adding or removing one ten.

Find 100 more or 100 less
Think about adding or removing one hundred.

Use place value mentally
Change the number without counting one by one.

Handle regrouping at boundaries
Understand cases such as 295 + 10 = 305 and 305 − 10 = 295.

For parents & teachers — standards alignment: This lesson directly addresses CCSS 2.NBT.B.8, which asks students to mentally add 10 or 100 to a given number from 100 through 900 and mentally subtract 10 or 100 from a given number from 100 through 900. Because the standard limits the given number, valid results can include 0 or 1,000 (for example, 100 − 100 = 0 and 900 + 100 = 1,000). Texas Grade 2 TEKS 2.7(B) extends the place-value relationship to finding the number that is 10 or 100 more or less than a given number up to 1,200. MathLattice keeps the core work here within the Grade 2 range through 1,000 and reserves the wider Texas range for the later state-extension lesson.

🧠 Key Vocabulary

more — a greater amount or value.

less — a smaller amount or value.

mental math — finding an answer in your head by using number relationships and efficient strategies.

place value — the value of a digit because of its position in a number.

regroup — rename equal place-value units, such as 10 tens as 1 hundred.

opposite changes — changes that undo each other, such as +10 and −10.

🔄 Four Place-Value Changes

10 more245 → 255

10 less245 → 235

100 more245 → 345

100 less245 → 145

Big idea: 10 more or less changes the number by one ten. 100 more or less changes the number by one hundred. Use place value first instead of counting forward or backward one by one.

🔟 Think in Tens

245

10 more→

255

245 has 4 tens. Ten more means one additional ten, so it becomes 5 tens: 245 + 10 = 255.

245

10 less→

235

Ten less removes one ten. The hundreds and ones digits stay the same here: 245 − 10 = 235.

💯 Think in Hundreds

245

100 more→

345

One hundred more adds one hundred: 245 + 100 = 345. The tens and ones digits stay 4 and 5.

245

100 less→

145

One hundred less removes one hundred: 245 − 100 = 145.

🏠 What Changes in the Place-Value Chart?

Change	Place-value action	Example
10 more	Add 1 ten	372 → 382
10 less	Remove 1 ten	678 → 668
100 more	Add 1 hundred	316 → 416
100 less	Remove 1 hundred	824 → 724

⚠️ Sometimes More Than One Digit Changes

A helpful pattern is that adding 10 keeps the ones digit the same and adding 100 keeps the tens and ones unchanged. But when a place fills or must be decomposed, more than one written digit can change.

295+10 → 305−10 → 295

In 295 + 10, 9 tens plus 1 ten make 10 tens, which regroup as 1 hundred. The 2 hundreds become 3 hundreds, the tens return to 0, and the 5 ones stay the same. That is why the result is 305.

Common mistake: “10 more” does not mean “make the tens digit one larger no matter what.” Place value is the rule. For example, 10 more than 295 is 305 because regrouping creates a new hundred.

↔️ Opposite Changes Undo Each Other

Ten more and ten less are opposites. One hundred more and one hundred less are opposites. This gives you a fast way to check your answer.

Check a 10-change
472 + 10 = 482, and 482 − 10 = 472.

Check a 100-change
635 + 100 = 735, and 735 − 100 = 635.

🌟 25 Worked Examples

Try each problem first. Then open “Show solution” to check the place-value reasoning.

1Find 10 more

What is 10 more than 245?

Show solutionHide solution

Adding 10 adds 1 ten. 245 + 10 = 255.

2Find 10 less

What is 10 less than 245?

Show solutionHide solution

Subtracting 10 removes 1 ten. 245 − 10 = 235.

3Find 100 more

What is 100 more than 245?

Show solutionHide solution

Adding 100 adds 1 hundred. 245 + 100 = 345.

4Find 100 less

What is 100 less than 245?

Show solutionHide solution

Subtracting 100 removes 1 hundred. 245 − 100 = 145.

5Ten more with the same ones digit

What is 10 more than 372?

Show solutionHide solution

372 + 10 = 382. The ones digit stays 2.

6Ten less with the same ones digit

What is 10 less than 678?

Show solutionHide solution

678 − 10 = 668. The ones digit stays 8.

7One hundred more keeps the tens and ones digits

What is 100 more than 316?

Show solutionHide solution

316 + 100 = 416. The tens and ones digits stay 1 and 6.

8One hundred less keeps the tens and ones digits

What is 100 less than 824?

Show solutionHide solution

824 − 100 = 724. The tens and ones digits stay 2 and 4.

9Cross a hundred with 10 more

What is 10 more than 295?

Show solutionHide solution

295 + 10 = 305. The ones digit stays 5. Nine tens plus 1 ten make 10 tens, which regroup as 1 hundred, so 2 hundreds become 3 hundreds and 0 tens remain.

10Cross a hundred with 10 less

What is 10 less than 305?

Show solutionHide solution

305 − 10 = 295. Decompose 1 of the 3 hundreds into 10 tens: 305 becomes 2 hundreds, 10 tens, and 5 ones. Remove 1 ten to get 2 hundreds, 9 tens, and 5 ones, or 295.

11Reach 1,000 with 100 more

What is 100 more than 900?

Show solutionHide solution

900 + 100 = 1,000. Ten hundreds make one thousand.

12Move from 100 to 0 with 100 less

What is 100 less than 100?

Show solutionHide solution

100 − 100 = 0. Removing the one hundred leaves zero.

13Move below 100 with 10 less

What is 10 less than 100?

Show solutionHide solution

100 − 10 = 90. Decompose 1 hundred as 10 tens, then remove 1 ten.

14Write a 10-more equation

Complete: 486 + 10 = ___.

Show solutionHide solution

486 + 10 = 496.

15Write a 10-less equation

Complete: 731 − 10 = ___.

Show solutionHide solution

731 − 10 = 721.

16Write a 100-more equation

Complete: 508 + 100 = ___.

Show solutionHide solution

508 + 100 = 608.

17Write a 100-less equation

Complete: 654 − 100 = ___.

Show solutionHide solution

654 − 100 = 554.

18Find the starting number

A number becomes 472 after adding 10. What was the starting number?

Show solutionHide solution

Think 10 less than 472: 472 − 10 = 462. Check: 462 + 10 = 472.

19Find the starting number with 100 more

A number becomes 683 after adding 100. What was the starting number?

Show solutionHide solution

Think 100 less than 683: 683 − 100 = 583.

20Choose the correct change

Which operation changes 427 to 527: 10 more, 10 less, 100 more, or 100 less?

Show solutionHide solution

527 is 100 greater than 427, so the change is 100 more.

21Choose the correct change

Which operation changes 764 to 754?

Show solutionHide solution

754 is 10 less than 764, so the change is 10 less.

22Compare two changes

Starting at 438, find 10 more and 100 more.

Show solutionHide solution

10 more is 448. 100 more is 538. The two changes affect different place values.

23Use two mental steps

Start at 625. Find 100 more, then 10 less.

Show solutionHide solution

625 + 100 = 725, then 725 − 10 = 715.

24Reverse a change

If 10 more than a number is 900, what is the number?

Show solutionHide solution

Find 10 less than 900: 900 − 10 = 890. Check: 890 + 10 = 900.

25Find and fix a place-value mistake

A student says 10 more than 356 is 456. What is the mistake?

Show solutionHide solution

456 is 100 more than 356. For 10 more, add 1 ten: 356 + 10 = 366.

🎮 Independent Practice — 30 Problems

1. What is 10 more than 234?
2. What is 10 less than 567?
3. What is 100 more than 321?
4. What is 100 less than 876?
5. What is 10 more than 489?
6. What is 10 less than 503?
7. What is 100 more than 700?
8. What is 100 less than 700?
9. Complete: 612 + 10 = ___.
10. Complete: 612 − 10 = ___.
11. Complete: 612 + 100 = ___.
12. Complete: 612 − 100 = ___.
13. What is 10 more than 890?
14. What is 100 more than 900?
15. What is 10 less than 100?
16. What is 100 less than 100?
17. A number becomes 458 after adding 10. What was the number?
18. A number becomes 745 after adding 100. What was the number?
19. Which change takes 328 to 338: 10 more, 10 less, 100 more, or 100 less?
20. Which change takes 684 to 584?
21. Which change takes 450 to 440?
22. Which change takes 517 to 617?
23. Start at 346. Find 10 more, then 10 more again.
24. Start at 346. Find 100 more, then 100 less.
25. Start at 590. Find 10 more, then 100 more.
26. Start at 810. Find 100 less, then 10 less.
27. Explain why 472 and 482 have the same ones digit when 482 is 10 more than 472.
28. Explain why 635 and 735 have the same tens and ones when 735 is 100 more than 635.
29. A student says 10 less than 402 is 302. Correct the mistake.
30. Extension challenge: A number is 100 less than 1,000 and 10 more than another number. Find both numbers.

🏆 Lesson Test — 15 Questions

1. What is 10 more than 357?
2. What is 10 less than 642?
3. What is 100 more than 415?
4. What is 100 less than 815?
5. What is 10 more than 895?
6. What is 10 less than 205?
7. Complete: 728 + 100 = ___.
8. Complete: 728 − 100 = ___.
9. What is 100 more than 900?
10. What is 10 less than 100?
11. A number becomes 673 after adding 10. What was the number?
12. Which change takes 546 to 446?
13. Start at 680. Find 10 more, then 100 more.
14. Correct the mistake: A student says 100 more than 274 is 284.
15. Explain why adding 10 to 398 gives 408 even though more than one digit changes.

🔐 Complete Answer Key

Show practice answer key Hide practice answer key

Practice Answers

Answer-key note: For explanation items, equivalent wording is acceptable when the place-value reasoning and final number are correct.

1. 244.

2. 557.

3. 421.

4. 776.

5. 499.

6. 493.

7. 800.

8. 600.

9. 622.

10. 602.

11. 712.

12. 512.

13. 900.

14. 1,000.

15. 90.

16. 0.

17. 448.

18. 645.

19. 10 more.

20. 100 less.

21. 10 less.

22. 100 more.

23. 356, then 366.

24. 446, then 346.

25. 600, then 700.

26. 710, then 700.

27. Adding 10 adds 1 ten and no ones, so the ones digit stays 2.

28. Adding 100 adds 1 hundred without changing the tens or ones, so both numbers end in 35.

29. 402 − 10 = 392. The student subtracted 100 instead of 10.

30. 100 less than 1,000 is 900. If 900 is 10 more than another number, that number is 890.

Show test answer key Hide test answer key

Test Answers

Answer-key note: For explanation items, equivalent wording is acceptable when the place-value reasoning and final number are correct.

1. 367.

2. 632.

3. 515.

4. 715.

5. 905.

6. 195.

7. 828.

8. 628.

9. 1,000.

10. 90.

11. 663.

12. 100 less.

13. 690, then 790.

14. 274 + 100 = 374. The student found 10 more instead of 100 more.

15. Adding 10 adds one ten. In 398, 9 tens plus 1 ten make 10 tens, which regroup as 1 hundred, so 398 + 10 = 408. The ones digit stays 8.

💡 Common Mistakes to Watch For

Confusing 10 and 100
356 + 10 is 366, while 356 + 100 is 456.

Changing the wrong place
Use the value being added or removed: one ten or one hundred.

Ignoring regrouping
295 + 10 crosses a hundred and becomes 305.

Counting by ones
Use the place-value relationship to find the answer mentally and efficiently.

Unit 1 complete: This lesson finishes the Grade 2 Numbers & Place Value unit. Next, Lesson 7 begins Addition & Subtraction Within 100 with Addition & Subtraction Fluency Within 20.

🔗 Related Lessons

Lesson 5 — Skip Count by 2s, 5s, 10s & 100s Review equal jumps of 10 and 100 before using them as mental place-value changes. Lesson 1 — Numbers to 1,000: Hundreds, Tens & Ones Review the value of each place before changing a number by one ten or one hundred. Grade 1 — 10 More, 10 Less & Number Patterns Review the earlier two-digit version of the 10-more and 10-less relationship.

🖨️ Printable Companion

A future 10 More, 10 Less, 100 More & 100 Less Practice Pack can include place-value charts, mental-math chains, missing-number puzzles, boundary cases, error-analysis tasks, mixed review, and a complete answer key.

← Lesson 5: Skip Count by 2s, 5s, 10s & 100s Grade 2 Math Hub Next: Addition & Subtraction Fluency Within 20 →