Estimation - First Grade
What is Estimation?
Concept: Estimation means making a smart guess about a number without counting exactly. It helps us find an answer that is close to the real answer!
Why Do We Estimate?
✓ To quickly find an answer without exact counting
✓ To check if our answer makes sense
✓ To make math easier and faster
✓ To use in real life (like guessing how many apples are in a basket)
💡 Tip: Estimation gives us a number that is "about" or "close to" the real answer!
Estimate to the Nearest Ten
Concept: Rounding to the nearest ten means finding which "ten" a number is closest to (10, 20, 30, 40, 50, 60, 70, 80, 90, 100...).
The Multiples of 10:
10
20
30
40
50
60
70
80
90
100
💡 Tip: These are our "landmark" numbers - we round to the closest one!
The Rounding Rule
Formula: Look at the ONES place digit to decide whether to round up or round down.
⬇️ Round DOWN
If the ones digit is:
0, 1, 2, 3, 4
Keep the tens place the same and change ones to 0
⬆️ Round UP
If the ones digit is:
5, 6, 7, 8, 9
Add 1 to tens place and change ones to 0
🎯 Remember: 5 and above, give it a shove (round up)!
4 and below, let it go (round down)!
💡 Tip: The number 5 is the magic number - it rounds UP!
Step-by-Step Method
How to Round to the Nearest Ten:
Step 1: Look at the number in the ONES place
Step 2: Is it 0, 1, 2, 3, or 4? → Round DOWN (keep tens the same)
Step 3: Is it 5, 6, 7, 8, or 9? → Round UP (add 1 to tens)
Step 4: Change the ones digit to 0
💡 Tip: Always look at the ones place first!
Examples: Rounding DOWN (0, 1, 2, 3, 4)
Example 1: Round 23 to the nearest ten
• Look at the ones place: 3
• Is 3 in the group (0, 1, 2, 3, 4)? YES!
• Round DOWN: Keep the 2 in tens place
23 rounds to 20
Example 2: Round 41 to the nearest ten
• Look at the ones place: 1
• Is 1 in the group (0, 1, 2, 3, 4)? YES!
• Round DOWN: Keep the 4 in tens place
41 rounds to 40
More Examples:
12 → 10
34 → 30
52 → 50
64 → 60
81 → 80
💡 Tip: When you round down, the answer is SMALLER than the original number!
Examples: Rounding UP (5, 6, 7, 8, 9)
Example 1: Round 27 to the nearest ten
• Look at the ones place: 7
• Is 7 in the group (5, 6, 7, 8, 9)? YES!
• Round UP: 2 + 1 = 3 in tens place
27 rounds to 30
Example 2: Round 55 to the nearest ten
• Look at the ones place: 5
• Is 5 in the group (5, 6, 7, 8, 9)? YES!
• Round UP: 5 + 1 = 6 in tens place
55 rounds to 60
More Examples:
16 → 20
38 → 40
49 → 50
65 → 70
78 → 80
89 → 90
💡 Tip: When you round up, the answer is BIGGER than the original number!
Using a Number Line
Visual Method: A number line helps us see which ten is closest!
Example: Round 46 to the nearest ten
40 — 41 — 42 — 43 — 44 — 45 — 46 — 47 — 48 — 49 — 50
↑ 46 is HERE ↑
• 46 is between 40 and 50
• Look at the ones digit: 6
• 6 is in the group (5, 6, 7, 8, 9) → Round UP!
46 rounds to 50
💡 Tip: Draw a number line to help you see which ten is closer!
Practice Problems
Problem 1: Round 32 to the nearest ten
Answer: 30 (ones digit is 2 → round down)
Problem 2: Round 58 to the nearest ten
Answer: 60 (ones digit is 8 → round up)
Problem 3: Round 74 to the nearest ten
Answer: 70 (ones digit is 4 → round down)
Problem 4: Round 85 to the nearest ten
Answer: 90 (ones digit is 5 → round up)
Problem 5: Round 91 to the nearest ten
Answer: 90 (ones digit is 1 → round down)
Problem 6: Round 67 to the nearest ten
Answer: 70 (ones digit is 7 → round up)
Quick Reference Chart
| Number | Ones Digit | Round To | Direction |
|---|---|---|---|
| 21 | 1 | 20 | Down ⬇️ |
| 37 | 7 | 40 | Up ⬆️ |
| 43 | 3 | 40 | Down ⬇️ |
| 55 | 5 | 60 | Up ⬆️ |
| 62 | 2 | 60 | Down ⬇️ |
| 89 | 9 | 90 | Up ⬆️ |
Important Vocabulary
- Estimate: A smart guess about how much or how many
- Round: To change a number to the nearest ten, hundred, etc.
- Nearest Ten: The multiple of 10 that is closest to a number
- Ones Place: The first digit from the right in a number
- Tens Place: The second digit from the right in a number
- Multiple of 10: Numbers like 10, 20, 30, 40, 50, 60, 70, 80, 90, 100
🎯 Tips for Estimation Success 🎯
- ✓ Always look at the ONES place digit first!
- ✓ Remember: 5 and above rounds UP, 4 and below rounds DOWN
- ✓ Draw a number line to help you visualize
- ✓ Use the rhyme: "5 and above, give it a shove!"
- ✓ Practice with real objects like toys or snacks
- ✓ Check your answer - does it make sense?
⭐ You're an Estimation Expert! ⭐
Great job learning to estimate to the nearest ten! This skill will help you solve problems faster and check your work. Keep practicing!