➕ Topic Summary
Estimating sums by rounding helps us find an approximate answer quickly. Instead of calculating the exact sum, we round each number to a specific place value (like the nearest ten, hundred, or thousand) and then add the rounded numbers. This gives us an estimate that is close to the actual sum.
For example, if you want to estimate $345 + 678$ by rounding to the nearest hundred, you would round $345$ to $300$ and $678$ to $700$. Then, you add $300 + 700$ to get an estimate of $1000$.
🧮 Part A: Vocabulary
Match the term with the correct definition:
| Term |
Definition |
| 1. Estimate |
A. The result of adding two or more numbers. |
| 2. Rounding |
B. Finding a number that is close to the exact number. |
| 3. Sum |
C. Adjusting a number to a nearby value based on a specific place value. |
| 4. Place Value |
D. The value of a digit based on its position in a number. |
| 5. Addend |
E. A number that is being added to another number. |
✍️ Part B: Fill in the Blanks
When we estimate sums by __________, we first adjust each number to the nearest ten, hundred, or __________. Then, we add the __________ numbers to find an __________ sum. This makes mental math much __________.
🤔 Part C: Critical Thinking
Explain a real-life situation where estimating sums by rounding would be useful. Give an example.