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:
Rounded to the nearest ten thousand, 53,478 is 60,000.
Corrected: Rounded to the nearest ten thousand, 53,478 is 50,000.
53,478 is between 50,000 and 60,000. The thousands digit is 3, so we round down to 50,000.
2. Fix the sentence:
The number 47,612 rounds to 40,000 to the nearest ten thousand.
Corrected: The number 47,612 rounds to 50,000 to the nearest ten thousand.
47,612 sits between 40,000 and 50,000. Because 7 is 5 or greater, we round up to 50,000.
3. Fix the sentence:
When we round 85,000 to the nearest ten thousand, we get 80,000.
Corrected: When we round 85,000 to the nearest ten thousand, we get 90,000.
When the thousands digit is 5, the rule is to round up. So 85,000 becomes 90,000.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Rounded to the nearest ten thousand, 32,189 is 30,000.
32,189 is closer to 30,000 than to 40,000, so it rounds down to 30,000.
2. Rounded to the nearest ten thousand, 76,540 is 80,000.
Since the thousands digit is 6, we round up. 76,540 becomes 80,000.
3. The number 14,999 rounds to 10,000 when rounded to the nearest ten thousand.
Only the thousands digit matters here. 4 is less than 5, so 14,999 rounds down to 10,000.
4. Rounded to the nearest ten thousand, 65,000 is 70,000.
When the thousands digit is 5, we round up. So 65,000 becomes 70,000.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Round 48,237 to the nearest ten thousand. Explain your reasoning.
Sample answer: 48,237 rounds to 50,000. The thousands digit is 8, which is 5 or greater, so I round up to the next ten thousand.
The thousands digit (8) is 5 or greater, so we round up from 40,000 to 50,000.
2. A stadium holds 27,500 fans. About how many is that, rounded to the nearest ten thousand?
Sample answer: It is about 30,000 fans. The thousands digit is 7, which is greater than 5, so 27,500 rounds up to 30,000.
Since the thousands digit is 7, we round up, giving an approximate value of 30,000.