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In this activity, we will be learning about estimation by rounding numbers to the nearest hundred or ten.
When rounding to the nearest ten, we look at the digit in the ones place.
If it is a 1, 2, 3, or 4, the number rounds down to the ten below.
If the digit in the ones place is a 5, 6, 7, 8 or 9, the number rounds up to the ten above.
So, 47 rounds up to 50 because there is a 7 in the ones place, but 43 rounds down to 40 because there is a 3 in the ones place.
When rounding to the nearest hundred, we look at the digit in the tens place.
If it is a 1, 2, 3 or 4, the number rounds down to the hundred below.
If it is a 5, 6, 7, 8 or 9, the number rounds up to the hundred above.
So, 386 rounds up to 400 because there is an 8 in the tens place, but 346 rounds down to 300 because there is a 4 in the tens place.
Example
Round these numbers to the nearest hundred so that the answer can be estimated.
| 321 + 689 | can be rounded to |
|
Estimated answer is C
Answer
A 321 rounds down to 300 to the nearest hundred
B 689 rounds up to 700 to the nearest hundred
C 300 + 700 = 1,000
Let's try some questions now!
