Rounding Off Decimals for Grade 5

1. By: Engr. Lovely Mae G. Gabayno
Are you ready?

2. By: Engr. Lovely Mae G. Gabayno

3. By: Engr. Lovely Mae G. Gabayno

4. By: Engr. Lovely Mae G. Gabayno

5. By: Engr. Lovely Mae G. Gabayno

6. By: Engr. Lovely Mae G. Gabayno

7. What is "Rounding" ?
Rounding means making a number simpler but keeping its value
close to what it was.
Example:
73 rounded to the nearest ten is 70, because 73 is closer to 70 than
to 80. But 76 goes up to 80.
Lightning McQueen
The result is less
accurate, but easier to
use.

8. Example: Round 74 to the nearest 10
We want to keep the "7" (it is in the 10s position)
The next digit is "4" which is less than 5, so no change is needed to "7"
Answer: 70 (74 gets "rounded down")
How to Round Numbers?
• Decide which is the last digit to keep
• Leave it the same if the next digit is less than 5 (this is called
rounding down)
• But increase it by 1 if the next digit is 5 or more (this is called
rounding up)
Luigi
Example: Round 86 to the nearest 10
We want to keep the "8"
The next digit is "6" which is 5 or more, so increase the "8" by 1 to "9"
Answer: 90 (86 gets "rounded up")
When the first digit removed
is 5 or more, increase the last
digit remaining by 1.

9. Think about sport: we should have the same number of players on each
team, right?
• 5 is in the middle ... so we could go up or down. But we need
a method that everyone agrees to.
• 0, 1, 2, 3 and 4 are on team "down"
• 5, 6, 7, 8 and 9 are on team "up"
Why does 5 go up ?
Tow Mater

10. Rounding Decimals
• First work out which number will be left when we finish.
• Rounding to tenths means to leave one number after the
decimal point.
• Rounding to hundredths means to leave two numbers after
the decimal point.
• etc.
Doc Hudson
3.1416 rounded to hundredths is 3.14
as the next digit (1) is less than 5
3.1416 rounded to thousandths is 3.142
as the next digit (6) is more than 5
1.2735 rounded to tenths is 1.3
as the next digit (7) is 5 or more
To round to "so many
decimal places" count that
many digits from the decimal
point:

11. Rounding to Significant Digits
• To round to "so many" significant digits, count digits from left
to right, and then round off from there.
1.239 rounded to 3 significant digits is 1.24
as the next digit (9) is 5 or more
134.9 rounded to 1 significant digit is 100
as the next digit (3) is less than 5
Chick Hicks
When there are leading zeros (such
as 0.006), don't count them
because they are only there to
show how small the number is:
0.0165 rounded to 2 significant digits is 0.017
as the next digit (5) is 5 or more

12. Rounding to Significant Digits
• To round to "so many" significant digits, count digits from left
to right, and then round off from there.
1.239 rounded to 3 significant digits is 1.24
as the next digit (9) is 5 or more
134.9 rounded to 1 significant digit is 100
as the next digit (3) is less than 5
When there are leading zeros (such as 0.006), don't count them
because they are only there to show how small the number is:
0.0165 rounded to 2 significant digits is 0.017
as the next digit (5) is 5 or more
Chick Hicks

13. 250.79
103.02
926.11
813.27
Solve these
problems!

14. THANK YOU FOR LISTENING! GOD BLESS YOU!!