Transcript Rounding Whole Numbers

Rounding Whole Numbers
• What is rounding? Rounding means
changing a given number to the nearest
ten, hundred, thousand, and so on.
• When rounding a number, you first need
to ask: what are you rounding it to?
Numbers can be rounded to the nearest
ten, the nearest hundred, the nearest
thousand, and so on.
To round a number to a given place:
• Step 1: Find the place you are rounding to: ten,
hundred, thousand or another place value.
ie: Round 6,458 to the nearest hundred - In
this case we are rounding to the hundred's
place.
• Step 2: Decide what two multiples the number
you are rounding is between.
ie: We are rounding to the hundred's place so
we would choose multiples of 100. So:
6,458 is between 6,400 and 6,500
• Step 3 Look at the digit to its right.
If the number you are rounding is followed by
5, 6, 7, 8, or 9, round the number up to the
higher multiple.
If the number you are rounding is followed by
0, 1, 2, 3, or 4, round the number down.
ie: Look in the ten place of the number 6,458.
We see a 5, so we must round to the higher
number.
Therefore: Round 6,458 to the nearest hundred
= 6,500
On a number line, you can see how rounding a
number approximates its value.
• You can use a number line to round a
whole number to a given place.
2,683
Round 2,683 to the nearest hundred.
First, find the rounding place.
2683
Hundreds
Then, find the number on a number
line.
2,683 is between 2600 and 2,700
• Round the number to the closest
hundred on the number line.
2,700 is the closest hundred.
Round 2,683 up to 2,700.
• Hint: If a number is located directly
in the middle of the number line,
round up.
 Round 13,528 to the nearest ten.
13,528
8>5
13,530
to 13,530
 Round 13,528 to the nearest hundred
13,528
2<5
13,500
to 13,500.
 Round 13,528 to the nearest thousand.
13,528
5=5
14,000
to 14,000
Round up
Round down
Round up
All the numbers to the right of the place you are
rounding to become zeros.
Consider the number 4,827.
– 4,827 rounded to the nearest ten is 4,830
– 4,827 rounded to the nearest hundred is 4,800
– 4,827 rounded to the nearest thousand is 5,000
Here are some more examples:
– 34 rounded to the nearest ten is 30
– 6,809 rounded to the nearest hundred is
6,800
– 1,951 rounded to the nearest thousand is
2,000
Why would you want to round a number?
Rounding is a form of estimation that you use when an
approximation is good enough.
For example when you are buying a TV at the store. The cost
might be marked at $279.00. You could say it is about $300.00.
Rounding is also good to use so that you know what to expect
for an answer. It is good to use this skill when you are plugging
numbers into a calculator.
Ex. Let's say you are adding up your expenses for the month.
Power: $230, Telephone: $79.68 Rent: $470 Car Payment:
$822. To get a good approximation of the money you will need
you could round to the closest hundred:
• Power: $230 would be$200
Phone $79.68 would be $100
Rent: $470 would be $500
Car: $822 would be $800
Total: $1601 which is close to the estimated total of $1600
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Activity
1. Round to the nearest thousand:
a) 14 389 ________ d) 9,520 _________
b) 29 610 ________ e) 56,239 _________
c) 3 492 ________ f) 89 743 _________
2. Round to the nearest ten thousand:
a) 24 987 _________ d) 24 033 _________
b) 37 096 _________ e) 295 474 _________
c) 145 302 _________ f) 77 330
_________
3. Round to
a) 89
b) 2 673
c) 265
the nearest ten:
_________ d) 514
_________ e) 97
_________ f) 2 753
_________
_________
_________
4. Round to
a) 847
b) 2 978
c) 5 048
5. Round
a) 929
b) 103
c) 965
the nearest hundred:
_________ d) 333
_________
_________
e) 5 496 _________
_________
f) 555
_________
to the nearest hundred thousand:
689 _________ d) 754 300 _________
232 _________ e) 222 678 _________
123 _________ f) 449 987 _________