Estimating differences by rounding involves approximating numbers to the nearest ten or hundred before subtracting. This makes mental math easier and helps us quickly find an approximate answer. For example, to estimate $48 - 23$, we can round $48$ to $50$ and $23$ to $20$, then subtract $50 - 20$ to get an estimate of $30$.
Rounding to the nearest ten means looking at the ones place. If it's 5 or more, we round up; if it's 4 or less, we round down. Similarly, rounding to the nearest hundred involves looking at the tens place.
Match the term with its definition:
| Term | Definition |
|---|---|
| 1. Estimate | A. The process of finding a number close to the exact answer. |
| 2. Rounding | B. The answer to a subtraction problem. |
| 3. Difference | C. To change a number to the nearest ten or hundred. |
| 4. Nearest Ten | D. The ten that a number is closest to. |
| 5. Nearest Hundred | E. The hundred that a number is closest to. |
Fill in the missing words in the following paragraph:
When we ___________ to the nearest ten, we look at the ___________ place. If the ones place is 5 or more, we round ___________. If it is 4 or less, we round ___________. Estimating differences by rounding makes subtraction easier to do in our ___________. For example, to estimate $77 - 32$, we round $77$ to $80$ and $32$ to $30$, and then subtract to get an estimate of ___________.
Explain in your own words why estimating differences by rounding can be helpful in everyday life. Provide at least two examples.
Estimating differences by rounding makes subtraction easier! Instead of working with exact numbers, we change them to the nearest ten or hundred. Then, we subtract the rounded numbers to get an estimate. This helps us quickly find an approximate answer. For example, to estimate $42 - 19$, we can round $42$ to $40$ and $19$ to $20$. The estimated difference is $40 - 20 = 20$.
Rounding is a useful skill in everyday life. When you're at the store, you can quickly estimate the total cost of items. It's also handy for checking if your exact calculations are reasonable. Happy rounding! 🧮
Match each term with its definition:
Use the words estimate, rounding, difference, ten, and hundred to complete the sentences.
When we don't need an exact answer, we can ________. This involves changing numbers to the nearest ________ or ________. The result of subtraction is called the ________. An ________ is an approximate calculation. ________ helps simplify calculations.
Explain a situation where estimating differences by rounding would be more useful than finding the exact answer. Give an example.
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