Adding & Subtracting Fractions confidential1 ROUNDING FRACTIONS & MIXED NUMBERS- ESTIMATING SUMS AND...
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Transcript of Adding & Subtracting Fractions confidential1 ROUNDING FRACTIONS & MIXED NUMBERS- ESTIMATING SUMS AND...
confidential 1Adding & Subtracting Fractions
ROUNDING FRACTIONS & MIXED NUMBERS- ESTIMATING SUMS
AND DIFFERENCES.
confidential 2Adding & Subtracting Fractions
REVIEW
• Write each fraction in simplest form a) 3 = 1 18 6 b) 21 = ¾ 28 c) 6 = 3 38 19
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Review
• Write each improper fractions as a mixed number
• 11 = 1 1 15 = 1 2
10 10 9 3
Find the LCD of 1 and 4 3 9 LCD = 9
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ROUNDING FRACTIONS AND MIXED NUMBERS
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ROUNDING FRACTIONS AND MIXED NUMBERS
• To round to the nearest half, we can use certain guidelines:
i) 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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Rounding fractions
ii) ROUND TO ½ : If the numerator is about half of the denominator, round the fraction to ½.
Example : 2 3 rounds to 2 ½ 8
3 is about half of 8
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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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Examples- Round to the nearest half
• Round 3 1 to the nearest half. 6 The numerator of 1 is much smaller than 6
the denominator. So 3 1 rounds to 3. 6
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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 8
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Example – 3
• Round 8 8 to the nearest half. 9
since the numerator of the fractional part is almost equal to the denominator.
So 8 8 rounds to 9. 9
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Your Turn
• Round each number to the nearest half• 8 1 = 8 12
2 9 = 3
10
5 = ½ 12
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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.
confidential 13Adding & Subtracting Fractions
confidential 14Adding & Subtracting Fractions
ESTIMATING SUMS AND DFFERENCES
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REVIEW
• Estimate using rounding:a) 2.3 + 7.9 + 4.1 = 2 + 8 + 4 = 14b) 9.3 – 4.758 = 9 – 5 = 4c) 12.006 + 5. 21 – 4.23 = 12 + 5 – 4
= 13
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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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Estimate Sums
☼ Estimate 5 + 11 8 12
5 rounds to ½ 8
11 Rounds to 1
12
5 + 11 = ½ + 1 = 1 ½
8 12
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Estimate Differences
Estimate 7 - 1
13 6
7 Rounds to ½
13
1 Rounds to 0
6
7 - 1 = ½ - 0 = ½
13 6
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Your Turn
• Estimate:1. 2 + 7 = ½ +1 = 1 ½ 5 82. 6 + 4 = ½ + ½ = 1 13 9 3. 9 - 4 = 1 – ½ = ½ 10 94. 6 - 3 = ½ - ½ = 0 9 7
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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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Example – Mixed Number Sum
• Estimate 4 5 + 2 1
6 5
4 5 rounds to 5. 2 1 rounds to 2
6 5
Estimate 5 – 2 = 7
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Example – Mixed Difference
• Estimate 2 5 - 2
8 5
2 5 - 2 = 2 ½ - ½ = 2 8 5
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Your turn
• Estimate• 3 1 + 1 5 = 3 + 2 = 5 8 6 2 7 - 1 8 = 3 – 2 = 1 8 9
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Let’s have fun
• http://www.thekidzpage.com/freekidsgames/xword/fairytalepuzzle.html
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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 = 13Border is about 10 + 10 + 13 + 13 =
46
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Your turn
• Estimate the perimeter of rectangle if length is 13 9 inches an breadth is 2 ¼ in
11Length = 14 and Breadth = 2Perimeter = 14 + 14 + 2+ 2 = 32
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Practice Problems
• Round each number to the nearest half
1. 2 4/5 = 3 2. 4 4/9 = 4 ½ 3. 6 11/12 = 7 4. 3 2/3 = 3 ½ 5. 6 1/7 = 6
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Practice Problems
• James walked 6 5 miles. To the nearest 8
half male, how many miles did she walk.
To the nearest half, he walked about 6 ½ miles.
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Practice Problems
• Estimatea. 9/10 – ½ = 1 – ½ = ½ b. 3/8 – 1/9 = ½ - 0 = ½c. 1 9/10 – 1 1/8 = 2 – 1 = 1d. 4 1/3 + 1 1/9 = 4 + 1 = 5e. 6 ¼ + 2 5/6 + 3 3/8 = 6 + 3 + 3 =
12
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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.
confidential 31Adding & Subtracting Fractions