Chris Clements

1
800
300
Rounding
To the nearest 100
100
700
Chris Clements
2
ltdategt
ltSteps to successgt
3
Rounding
Rounding
Rounding
Rounding
Rounding is used to approximate or estimate.
In this lesson we are looking at rounding numbers
to the nearest 100.
4
Rounding whole numbers
Rounding whole numbers
Can you remember how to round numbers to the
nearest 10?
Identify the units digit.
If the units digit is a 1, 2, 3 or 4 we round
down.
If the units digit is a 5, 6, 7, 8, or 9 we
round up.
5
3
9
3
2
3
7
5
5
7
2
8
2
9
.
1
8
5
8
continued
6
Onto the next step.
2) If the tens digit is a 0, 1, 2, 3 or 4 we
round down to the nearest 100.


510 520 530 540 550 560 570 580 590
600
500
0
5
4
4
Is it closer to 500 or 600?
0
5
0
round down


410 420 430 440 450 460 470 480 490
500
400
3
4
2
2
Is it closer to 400 or 500?
0
4
0
round down
Can you see that the units digit is not important
when rounding numbers to 100?
continued
7
Onto the final step.
3) If the tens digit is a 5, 6, 7, 8 or a 9
round up to the next hundred.


510 520 530 540 550 560 570 580 590
600
500
0
5
5
5
0
6
0
Is it closer to 500 or 600?
round up


610 620 630 640 650 660 670 680 690
700
600
3
6
8
8
Is it closer to 600 or 700?
0
7
0
round up
Remember if a number ends in -50, although it is
exactly halfway between the two hundred values we
still round up!
continued
8
Lets have ago at rounding to the nearest 100.


310 320 330 340 350 360 370 380 390
400
300
4
3
2
2
Is it closer to 300 or 400?
0
3
0
round down


610 620 630 640 650 660 670 680 690
700
600
8
6
5
5
Is it closer to 600 or 700?
0
7
0
round up


710 720 730 740 750 760 770 780 790
800
700
0
3
7
0
Is it closer to 700 or 800?
7
0
0
round down
continued
9
And more


110 120 130 140 150 160 170 180 190
200
100
9
1
4
4
Is it closer to 100 or 200?
0
1
0
round down


810 820 830 840 850 860 870 880 890
900
800
8
8
8
8
Is it closer to 800 or 900?
0
9
0
round up


910 920 930 940 950 960 970 980 990
1000
900
5
1
9
5
Is it closer to 900 or 1000?
0
0
0
1
round up
10


9
4
7
7
0
5
0


0
2
0
7
2
1
1


0
9
0
1
8
6
6
continued
11
Last three


9
2
4
4
0
2
0


0
6
0
8
5
7
7


0
9
0
9
9
0
0
continued
12
Activity
lttype heregt
13
ltdategt
Steps to success

1. Identify the tens digit.

2) If the tens digit is a 0,1, 2, 3 or 4 we
round down to the nearest 100.
3) If the tens digit is a 5, 6, 7, 8 or a 9
round up to the next hundred.
14
Plenary
Match these numbers to the nearest 100.
490
428 700 342 100 712 400 51 300
170 and 320 490
170
420
320
390
How do you round numbers to the nearest thousand
(1000)?