Transcript PERCENTAGES

PERCENTAGES
Introduction
Percentages are a special type of fraction
based on 100 with their own language and
symbols............
• The symbol % means percent.
• 1% is defined as 1/100 (“one-hundredth”).
• To find 1% of a quantity simply divide by 100.
Percentages are Fraction !
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Remember, a percentage is a fraction based
on 100, you can use your fraction knowledge..
Can you fill in the gaps below ?
1% = 1/100 (“one-hundredth”)
23% = 23/100 (“twenty-three hundredths”)
39% =
50% = 50/100 = 1/2
75% =
Percentages as Fractions !
Remember, a percentage is a fraction based
on 100, you can use your fraction knowledge..
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1% = 1/100 (“one-hundredth”)
23% = 23/100 (“twenty-three hundredths”)
39% = 39/100 (“thirty-nine hundredths”)
50% = 50/100 = 1/2
75% = 75/100 = 3/4 (“three-quarters”)
Quick Exercise
Write the following fractions as percentages.....
1) 10/100
4) 41/100
2) 40/200
5) 54/600
3) 49/700
6) 64/800
Write the following percentages as fractions ...
1) 3%
4) 25%
2) 83%
5) 50%
3) 40%
6) 75%
Quick Exercise
Write the following fractions as percentages.....
1) 10/100 = 10%
4) 41/100 = 41%
2) 40/200 = 20%
5) 54/600 = 9%
3) 49/700 = 7%
6) 64/800 = 8%
Write the following percentages as fractions ...
1) 3% = 3/100
4) 25% = 1/4
2) 83% = 83/100
5) 50% = 1/2
3) 40% = 4/10
6) 75% = 3/4
Finding Percentages of Quantities
Question Find 42% of 240
• Divide 240 by 100 to find 1% = 2.4
• 42% = 42 x 1% = 42 x 2.4 = 100.8
Question Find 77% of 413
• Divide 413 by 100 to find 1% = 4.13
• 77% = 77 x 1% = 77 x 4.13 = 318.01
In percentages everything works around 100 !
Finding Percentages Questions
Find the following amounts ...
1) 25% of 500
4) 50% of 112
2) 30% of 170
5) 75% of 1200
3) 45% of 624
6) 90% of 6300
Percentages are sometimes used to increase or
decrease amounts...try these questions
1) Increase 200 by 12%
2) Decrease 450 by 10%
Finding Percentages Questions
Find the following amounts ...
1) 25% of 500 = 125
4) 50% of 112 = 56
2) 30% of 170 = 51
5) 75% of 1200 = 900
3) 45% of 624 = 280.8
6) 90% of 6300 = 5670
Percentages are sometimes used to increase or
decrease amounts...try these questions
1) Increase 200 by 12%
1% = 2, 12% = 24, add increase = 224
2) Decrease 450 by 10%
1% = 4.5, 10% = 45, subtract decrease = 405
SUMMARY
• Percentages are special fractions based on 100
• 1% means 1/100 “one-hundredth”.
• Cent.. means 100 e.g. Century, Centimetre.
• Percentages are used to find parts of a whole,
and to increase or decrease quanitities.