B. Number · Number Sense: Numbers to 10 000, Fractions and Decimal TenthsRounding to the Nearest Ten, Hundred or Thousand
B1.3About 35 minutes
Learning goals- I can round a number to the nearest ten, hundred or thousand.
- I can use a number line to find the closer ten, hundred or thousand.
- I can round numbers that are exactly halfway.
- I can decide when rounding makes sense.
Words to know
round
Change a number to a nearby friendly number that is easier to use.
nearest thousand
The closest multiple of 1000, like 4000 for 3820.
halfway
Exactly in the middle. 3500 is halfway between 3000 and 4000.
about
Close to, but not exact.
Remember from Grade 3
In Grade 3 you rounded to the nearest ten and the nearest hundred. You found the two tens (or hundreds) a number is between, and picked the closer one. When a number was exactly halfway, you rounded up. This year, you'll also round to the nearest thousand.
Let's start with a story
A newspaper says: "About 3000 people came to the winter skating party in our town." The real count was 2846.
The newspaper rounded 2846 to the nearest thousand. 2846 is between 2000 and 3000, and it is closer to 3000.
Rounding to the nearest thousand
- Find the two thousands the number is between.
- Find the halfway point. It ends in 500 (like 2500).
- Below halfway: round down. Halfway or above: round up.
A quick way: look at the hundreds digit. 0 to 4: round down. 5 to 9: round up.
| Round to the nearest... | Look at this digit | Example: 4682 |
|---|
| ten | ones | 4680 (2 ones: round down) |
| hundred | tens | 4700 (8 tens: round up) |
| thousand | hundreds | 5000 (6 hundreds: round up) |
Worked exampleExample 1: One number, three roundings
Round 4682 to the nearest ten, hundred and thousand.
- Nearest ten: 4682 is between 4680 and 4690. 2 ones is less than 5, so round down: 4680.
- Nearest hundred: between 4600 and 4700. 8 tens is 5 or more, so round up: 4700.
- Nearest thousand: between 4000 and 5000. 6 hundreds is 5 or more, so round up: 5000.
4680, 4700 and 5000. Always check which place the question asks for!
Worked exampleExample 2: Exactly halfway
Round 7500 to the nearest thousand.
- 7500 is between 7000 and 8000.
- 7500 is exactly halfway.
- When a number is halfway, we round up.
Worked exampleExample 3: Rounding up to 10 000
Round 9650 to the nearest thousand.
- 9650 is between 9000 and the next thousand, which is 10 000.
- 6 hundreds: round up.
Worked exampleExample 4: Careful with zeros
Round 6049 to the nearest hundred.
- 6049 is between 6000 and 6100.
- The tens digit is 4, so round down.
6000. (Not 6050: when rounding to hundreds, the answer must end in 00.)
When does rounding make sense?
Round when about is good enough: how many people came to a fair, how far a trip is, about how much a big item costs.
Don't round when you need an exact number, like the money you pay at a store, or labels like a house number or a phone number.
Just for funQ: What did 2846 say to 3000?
A: "I'm past halfway, so I'm close enough. Round me up!"
Hands-on activityRound the kilometres
You need: a map app or paper map (with a grown-up), or a list of distances your grown-up writes down, paper and a pencil.
- With a grown-up, find the driving distance in kilometres from your home to 4 or 5 faraway places (other cities, a cottage, relatives' homes). Choose some that are more than 1000 km away if you can. If you can't look them up, use these: 1352 km, 2786 km, 4495 km, 908 km, 5500 km.
- Make a chart: Distance, Nearest hundred, Nearest thousand.
- Fill in the chart.
- Explain to your grown-up which rounding you'd use to tell a friend "how far", and why.
Check: 1352 → 1400 and 1000; 2786 → 2800 and 3000; 4495 → 4500 and 4000; 908 → 900 and 1000; 5500 → 5500 and 6000.
Your turn
1Round 3271 to the nearest thousand.
3000. The hundreds digit is 2, so round down.
2Round 3271 to the nearest hundred.
3300. The tens digit is 7, so round up.
3Round 3271 to the nearest ten.
3270. The ones digit is 1, so round down.
4Round 6500 to the nearest thousand.
7000. It is exactly halfway, so round up.
5Round 8960 to the nearest hundred.
9000. It is between 8900 and 9000, and 6 tens means round up.
6Round 9512 to the nearest thousand.
10 000. 5 hundreds means round up.
7Should you round your phone number? Why or why not?
No. A phone number is a label. Changing it would call a different phone!
More practice: warm-up
1Round 4100 to the nearest thousand.
2Round 4900 to the nearest thousand.
3Round 2340 to the nearest hundred.
4Round 5678 to the nearest ten.
5What is halfway between 6000 and 7000?
More practice: on your own
1Round 7449 to the nearest thousand.
7000. The hundreds digit is 4, so it is below halfway (7500).
2Round 3095 to the nearest ten.
3100. It is between 3090 and 3100; 5 ones means round up.
3Round 1550 to the nearest hundred and to the nearest thousand.
Nearest hundred: 1600 (5 tens, round up). Nearest thousand: 2000 (5 hundreds, round up).
4A library has 6438 books. About how many is that, to the nearest thousand? To the nearest hundred?
Nearest thousand: 6000. Nearest hundred: 6400.
5Write a number that rounds to 5000 when rounded to the nearest thousand, but is greater than 5000.
Any number from 5001 to 5499. Example: 5300.
Challenge
1What is the least and the greatest whole number that rounds to 8000 (nearest thousand)?
Least: 7500 (halfway rounds up). Greatest: 8499 (8500 would round up to 9000).
2A number rounds to 3500 (nearest hundred) and to 4000 (nearest thousand). Give two possible numbers.
It must be from 3500 to 3549 to round to 3500, and at least 3500 to round to 4000. So any number from 3500 to 3549 works, for example 3520 and 3549.
3Lea rounded 4962 to the nearest hundred and got 5900. What went wrong? What is the right answer?
She changed the thousands digit instead of the hundreds digit. 4962 is between 4900 and 5000. 6 tens means round up to 5000.
Quiz
1. Round 5730 to the nearest thousand.
2. Round 2449 to the nearest hundred.
3. Round 8500 to the nearest thousand.
4. Round 6996 to the nearest ten.
5. Which number rounds to 4000 (nearest thousand)?
6. When does rounding make sense?
Big idea: B1.3 asks Grade 4 students to round whole numbers to the nearest ten, hundred or thousand in various contexts. Rounding is the base of estimation, which children use to check their calculations.
Common difficulties:
- Looking at the wrong digit. To round to the nearest thousand, look at the hundreds digit. Have your child underline the place they are rounding to and circle the digit to its right.
- Changing digits that should become zero (4682 to the nearest hundred written as 4782 or 4702). Remind them every digit after the rounding place becomes 0.
- Rounding across a thousand (8960 to 9000, 9650 to 10 000).
How to help: Always connect the shortcut to a number line so your child understands why ("Which thousand is closer?"). Use real contexts: distances on road signs, crowd sizes in the news, the cost of big items.