1. ROUNDING FRACTIONS & MIXED NUMBERS- ESTIMATING SUMS AND DIFFERENCES.
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2. REVIEW Write each fraction in simplest form a) 3 = 1 18 6 b) 21 = ¾ 28
b) 21 = ¾ 28
c) 6 = 3
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3. Review Write each improper fractions as a mixed number
11 = = 1 2
Find the LCD of 1 and 4
LCD = 9
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4. ROUNDING FRACTIONS AND MIXED NUMBERS
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5. ROUNDING FRACTIONS AND MIXED NUMBERS
To round to the nearest half, we can use certain guidelines:
ROUND UP : If the numerator is almost as large as the denominator, round the number up to the next whole number.
Example: 7 rounds to 1 8
7 is almost as large as 8.
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6. Rounding fractions
ii) ROUND TO ½ : If the numerator is about half of the denominator, round the fraction to ½.
Example : rounds to 2 ½ 8
3 is about half of 8
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7. ROUNDING FRACTIONS
iii) ROUND DOWN : If the numerator is much smaller than the denominator, round the number down to the whole number.
Example: 1/8 rounds to 0.
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8. Examples- Round to the nearest half6
The numerator of 1 is much smaller than
the denominator. So rounds to 3.
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9. Example – 2 Round 1 5 to the nearest half. 8
The numerator 5 is about half of the denominator 8. So, 1 5 = 1 ½
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10. Example – 3 Round 8 8 to the nearest half. 9
since the numerator of the fractional part is almost equal to the denominator.
So rounds to 9.
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11. Your Turn Round each number to the nearest half 8 1 = 8 12 2 9 = 3 10
= 8 12 = 10
= ½
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12. Use rounding to solve a problem
If you need 1 ¼ kilograms of flour needed to make sweets, should you buy 1 ½ kilograms or 1 kilogram?
Answer : Since 1 kilogram is less than 1¼ kilograms, we should round up and
buy 1 ½ kilograms.
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13. BREAK
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14. ESTIMATING SUMS AND DFFERENCES
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15. REVIEW Estimate using rounding: a) 2.3 + 7.9 + 4.1 = 2 + 8 + 4 = 14
b) 9.3 – = 9 – 5 = 4
c) – 4.23 = – 4 = 13
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16. Estimating Sums and Differences
We can estimate sums and differences of fractions by rounding each fraction to the nearest half. Then add or subtract.
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17. Estimate Sums ☼ Estimate 5 + 11 8 12 5 + 11 = ½ + 1 = 1 ½ 8 12
5 rounds to ½ 8
11 Rounds to 1 12
= ½ + 1 = 1 ½
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18. Estimate Differences Estimate 7 - 1 13 6 7 Rounds to ½ 13
7 Rounds to ½ 13
1 Rounds to 0 6
= ½ - 0 = ½
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19. Your Turn Estimate: 1. 2 + 7 = ½ +1 = 1 ½ 5 8 2. 6 + 4 = ½ + ½ = 1
= ½ +1 = 1 ½
= ½ + ½ = 1
= 1 – ½ = ½
= ½ - ½ = 0
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20. Mixed Number Sum And Differences
We can estimate sums and differences of mixed numbers by rounding each number to the nearest whole number.
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21. Example – Mixed Number Sum
Estimate
4 5 rounds to rounds to 2
Estimate 5 – 2 = 7
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22. Example – Mixed Difference
Estimate
= 2 ½ - ½ = 2
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23. Your turn Estimate 3 1 + 1 5 = 3 + 2 = 5 8 6 2 7 - 1 8 = 3 – 2 = 1 8 9
= = 5
= 3 – 2 = 1
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24. Let’s have fun
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25. Round up to solve a problem
The width of a room is 9 ¼ feet and length of a room is 12 ½ feet. About how much border the room will have?
Width = 10 feet Length = 13
Border is about = 46
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26. Your turn
Estimate the perimeter of rectangle if length is inches an breadth is 2 ¼ in 11
Length = 14 and Breadth = 2
Perimeter = = 32
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27. Practice Problems Round each number to the nearest half 1. 2 4/5 = 3
/5 = 3
/9 = 4 ½
/12 = 7
/3 = 3 ½
5. 6 1/7 = 6
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28. Practice Problems James walked 6 5 miles. To the nearest8
half male, how many miles did she walk.
To the nearest half, he walked about 6 ½ miles.
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29. Practice Problems Estimate 9/10 – ½ = 1 – ½ = ½ 3/8 – 1/9 = ½ - 0 = ½
9/10 – ½ = 1 – ½ = ½
3/8 – 1/9 = ½ - 0 = ½
1 9/10 – 1 1/8 = 2 – 1 = 1
4 1/ /9 = = 5
6 ¼ + 2 5/ /8 = = 12
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30. Review To round to the nearest half:
If the numerator s almost as large as the denominator, round the number to the nearest half
If the numerator is about half of the denominator, round the fraction to ½.
If the numerator is much smaller than the denominator, round the number down to the whole number.
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31. That's all for today
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