Transcript Rounding to nearest 10

Rounding to nearest 10
Rounding
Rounding helps us count easily in tens and hundreds.
If Bartosh has 7 toy cars, he might say
“I have almost 10 cars”,
because 7 is close to 10.
1 2 3 4 5 6 7 8 9 10
Rounding tens
Counting in tens is easy. Try this number line:
10 20 30 40 50 60 70 80 90 100 110
Complete these number sentences:
20 + 80 = 100
20 – 10 = 10
80 + 30 = 110
90 – 40 = 50
30 + 50 = 80
110 – 20 = 90
Rounding tens
How do we know what to round to?
0
1
2
3
4
5
6
7
8
9 10
These numbers
round up
These numbers
round down
What would we round 7 to?
0
1
2
3
4
5
6
7
8
9 10
Rounding tens
What would we round 37 to?
30 31 32 33 34 35 36 37 38 39 40
What would we round 73 to?
70 71 72 73 74 75 76 77 78 79 80
What would we round 55 to?
50 51 52 53 54 55 56 57 58 59 60
Rounding tens
What are the smallest and largest numbers that you
could round to 40?
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
There is always a difference of 9
between the smallest and the largest.
Smallest possible Rounded number Largest possible
75
84
80
45
54
50
15
24
20
85
94
90
Rounding tens
Round these numbers to the nearest ten.
68
70
13
10
44
40
25
30
79
80
87
90
92
90
55
60