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Percentages without a calculator

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Presentation on theme: "Percentages without a calculator"— Presentation transcript:

1 Percentages without a calculator
What is a Percentage Percentage as a Fraction Simplify Answer Percentage to a Decimal Fraction to a Percentage Percentages and Common Fractions Match Percentages to Common Fractions Use Common Fraction to solve a Perentage Finding 5%

2 What is a Percentage 3 5 or Which is the bigger 5 9
Difficult to tell without “ doing some Maths” To make comparing fractions ( part of ) easier a special fraction called a Percentage was introduced 7 Percentage is a fraction out of 100 7 per cent is written as 7% and equals 100

3 What is a percentage C 7 8 9 4 5 6 x 1 2 3 + . = - % means out of 100
38 38 38% means Out of 100 100 Ans C 7 8 9 ÷ Type in a number for the percentage then click the arrow 4 5 6 x 1 2 3 + 38 38 % is 100 . = - On Setup 38

4 What is a percentage 2 C 7 8 9 4 5 6 x 1 2 3 + . = -
% means out of 100 32 32 32% means Out of 100 100 2 Ans C 7 8 9 ÷ 4 5 6 x ÷ 2 ÷2 32 16 8 32 % is 1 2 3 + = = 100 50 25 ÷ 2 ÷2 . = - On 32 Setup Hide Fraction

5 Percentage to a decimal
To change a percentage to a decimal divide the number in front of the % by 100 28% = 28 ÷ 100 = 0.28 7% = 7 ÷ 100 = 0.07 91% = 91 ÷ 100 = 0.91 Changing a percentage to a decimal is like changing pence to pounds The next slide allows you to practice. Type a whole number for the percentage on the calculator then click the arrow

6 Percentage to a Decimal
10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 Enlarge 8% = 8 ÷ 100 = 0.08 Hide Scale (-) C x ÷ 8÷100 5 6 7 8 9 + - On Setup 0.08 11 1 2 3 4 . = Ans

7 Fraction to a Percentage
Step 1 : Change the Fraction to a decimal by dividing the top number by the bottom 5 = 5 ÷ 8 = 0.625 8 Step 2 : To change the decimal to a percentage multiply by 100 and add the % sign 0.625 x 100% = 62.5 % (-) C x ÷ Ansx100 Start Next 5 6 7 8 9 + - On 62.5 11 1 2 3 4 . = Ans

8 Fraction to a Percentage
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9 80% 81% 82% 83% 84% 85% 86% 87% 88% 89% 90% 4 = = % = % = 5 (-) C x ÷ Hide Scale Next 5 6 7 8 9 + - On Setup 11 1 2 3 4 . = Ans

9 Percentages and Common Fractions
20 % of Percentage 20% 20 Fraction = 1% 5% 10% 20% 25% 33⅓% 50% 66⅔% Ans C 1%m 5%m mult mult mult mult 7 8 9 ÷ 4 5 6 x 1 2 3 + Click a Percentage then enter the equivalent Fraction . = - On Setup

10 Match % to Fraction 20% 1% 10% 25% 33⅓% 50% 66⅔% 75% test Start

11 Percentages and Common Fractions
25% 1 Fraction = 25% 4 302÷4 1% 5% 10% 20% 25% 33⅓% 50% 66⅔% 75.5 1%m 5%m mult mult mult mult Ans C 25 % of 187.2 8 9 1 7 ÷ = x 187.2 4 5 6 x 4 1 2 3 + = . = - = On Setup New Example

12 Calculating 5% All All 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 24 12 12 5% of 240 = (a) 10% of 240= (b) = 5% of 240= (-) C x ÷ 5 6 7 8 9 + - On Find 10% then half the answer Next 11 1 2 3 4 . = Ans

13 Finding 5% 1 The fraction for 5% is 20 1 1 5% of 630 = = 630 of 630 ÷
x =31.5 20 20 Dividing by 20 can be done in two steps Step 1 Dividing by 10 Step 1 Find 10% Which is the same as 630÷10=63 Step 2 Dividing by 2 Step 1 Half to find 5% 63÷2=31.5 Divide by Bottom Multiply by Top See Next slide


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