Rounding Whole Numbers - Bridge Method
The Bridge Method is one way to round numbers
Bridge Components
Bottom Number
Top Number
Middle Number
76
Example
Rounding to the nearest 10’s
1 Focus in on the digit in the number based on what you are rounding to.
76
2 Place that digit on the Bottom Number part of the bridge
7
Bottom Number
3 Look at the number you are rounding. Count the number of digits after the selected digit you
focused on. Turn those into zeros and place them after the selected digit that you have focused
on.
76
there is on one digit after
7 which is 6.
The
6 becomes 0
70
Bottom Number
4 Because you are round to the nearest 10’s, you are actually counting by 10’s. Therefore all you
need to do is take your bottom number and add 10 to this to get the top number.
70 + 10 = 80
70
80
Bottom Number
Top Number
5 Knowing the Bottom Number and the Top Number allows you to figure out the Middle Number
(half way between. In our example the number would be
75
70
Bottom Number
75
80
Top Number
Middle Number
Rounding Whole Numbers - Bridge Method
6 With all the numbers in place on the bridge, the Bottom Number, Middle Number and Top
Number, the number being rounded can be placed onto the bridge
76
70
75
Bottom Number
76
80
Top Number
Middle Number
7 Now that the bridge is complete you can round the number up to the Top Number or down to
the Bottom Number. In our example the number
76 will be rounded up to 80 because 76 is
to the right of the Middle Number 75
70
75
Bottom Number
Middle Number
8 Therefore, rounding the number
76
80
Top Number
76 to the nearest 10’s would be 80.
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Activity
Round the number 76 to the nearest 10’s using the Bridge Method.
________
Round the number 84 to the nearest 10’s using the Bridge Method.
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Round the number 127 to the nearest 10’s using the Bridge Method.
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