Estimation and Rounding — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Grade 4 rounding shows 347 to the nearest 100 is 400.
Corrected: Grade 4 rounding shows 347 to the nearest 100 is 300.
The tens digit in 347 is 4, which is less than 5, so 347 rounds down to 300.
2. Fix the sentence:
In Grade 4, 567 rounded to the nearest 100 is 500.
Corrected: In Grade 4, 567 rounded to the nearest 100 is 600.
The tens digit in 567 is 6, which is 5 or more, so 567 rounds up to 600.
3. Fix the sentence:
Grade 4 students say 250 rounds to the nearest 100 as 200.
Corrected: Grade 4 students say 250 rounds to the nearest 100 as 300.
The tens digit is 5, and the 5-or-more rule rounds 250 up to 300.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Grade 4: 482 rounded to the nearest 100 is 500.
With a tens digit of 8, 482 rounds up to the next hundred, 500.
2. Grade 4: 731 rounded to the nearest 100 equals 700.
Since 3 is less than 5, 731 rounds down to 700.
3. In Grade 4, 950 rounded to the nearest 100 is 1000.
Using the 5-or-more rule, 950 rounds up to 1,000.
4. A Grade 4 student rounds 149 to the nearest 100 and gets 100.
Because 4 is less than 5, 149 rounds down to 100.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Describe how a Grade 4 student rounds 638 to the nearest 100.
Sample answer: I look at the tens digit, which is 3. Because 3 is less than 5, I round down. So 638 rounds to 600.
When rounding to the nearest 100, the tens digit decides the direction. A tens digit of 3 rounds 638 down to 600.
2. In Grade 4, why does 850 round up to 900 to the nearest 100?
Sample answer: The tens digit is 5. Because 5 means round up, 850 becomes 900.
A tens digit of exactly 5 rounds the number up, so 850 rounds to 900.