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Calculating in Construction - Percentages Percentages Lesson Focus This lesson is to help learners understand and calculate using percentages. Lesson Plan includes: Lesson instructions for trainers Worksheet 1 and 2 and answers Knowledge of the following numeracy skills: Ability to use a calculator for basic operations Ability to read decimals and understand the place value of the digits How this maths skill can be reinforced on the job: In Construction, an understanding of the basic number concepts associated with percentages are beneficial across many areas in the workplace, such as when calculating and estimating quantities, calculating wastage, working with customer invoices, trade discounts, GST and so on. Lesson time: Approximately 30 minutes Materials needed for this lesson: Worksheets for each learner Calculator for each learner Whiteboard . Lesson breakdown: Suggested delivery strategy: Step Trainer/Learner Activity 1 Introduction to “percentage” 2 Calculating a percentage of an amount Worksheet 1 – Learners complete with trainer support / answers 3 available 4 Strategies for common percentages: Calculating 10%, 20%, 30%, 40%, 50% 5 Strategies for common percentages: Calculating 25%, 50%, 75% 6 Strategies for common percentages: Other simple percentages. 7 Worksheets – Learners complete with trainer support / answers available Construction Skills Queensland – Integrated LLN and Learning Support Strategy 1 Calculating in Construction - Percentages 1. Introduction to percentages Discuss the following ideas about percentages with the learners. A percentage refers to part of a whole amount where the whole amount is 100%. So every time a percentage is stated it is like an amount out of 100. Write the following examples on the board. Example 1 Suppose 20% of our group live on their own. What does this mean? The whole group is 100%. Of the whole group 20% live on their own. This tells us that 20 out of 100 people in our group live alone. Note that our group does not have 100 people in it, but if we think of the whole group as 100%, then if our group did have 100 people in it 20 of them would live alone. Example 2 Suppose 10% of our group were “mature age”? What does this mean? 10% means 10 out of every 100, or 1 out of 10. 1 in every 10 of the group is mature age. Note that our group does not have 100 people in it, but if we think of the whole group as 100%, then if our group did have 100 people in it 10 of them would be mature age. Example 3 Suppose only 25% of customers pay cash. What does this mean? 25% means 25 out of every 100, or 1 out of 4. Only 1 out of every 4 customers pay cash. Note that we may not have 100 customers, but if we think of the whole group as 100%, then for every 100 customers we have, 25 of them would pay cash. Construction Skills Queensland – Integrated LLN and Learning Support Strategy 2 Calculating in Construction - Percentages 2. Calculating a percentage of an amount Explain the following method of calculating a percentage. Work through the examples with the learners. For example, what is 25 kg as a percentage of 400 kg? Divide the 25 by the larger amount 400. Answer is 0.0625 To write this as a percentage, multiply by 100 0.0625 x 100 = 6.25 Your answer is 6.25% For example, what percentage of $60 is $3? Divide the 3 by the larger amount 60. Answer is 0.05 To write this as a percentage, multiply by 100 0.05 x 100 = 5 Your answer is 5% For example, what percentage of 10m out of 80m? Divide the 10 by 80. Answer is 0.125 To write this as a percentage, multiply by 100 0.125 x 100 = 12.5 Your answer is 12.5% For example, what percentage is 120 mm out of 4 m? Because mm and m are different units, we need to change one of them so they are both the same. In this instance, it is easiest to change 4m to 4 000 mm. Divide the 120 by the larger amount 4 000. Answer is 0.03 To write this as a percentage, multiply by 100 0.03 x 100 = 3 Your answer is 3% 3. Learners complete Worksheet 1 with trainer support and answers. Construction Skills Queensland – Integrated LLN and Learning Support Strategy 3 Calculating in Construction - Percentages 4. Calculating 10%, 20%, 30%, 40%, 50%. Explain to learners that some percentages are easy to find if you know certain tips. You are going to show them some of the simple ways of finding percentages. To find 10% of an amount 10% means 10 out of 100, or 1 out of 10. To find 10% of something, just move the decimal one place to the left. For example, 10% of $260.00 = $26.00 10% of 95 kg = 9.5 kg 10% of 1462 m = 146.2 m To find 20%, 30%, 40% or 50% Find 10%, then multiply by 2, 3, 4, or 5 etc to get 20%, 30%, 40% or 50%. Examples To find 20% of $260.00 10% of $260.00 = $26.00 Multiply $26 by 2 to find 20% Answer is $52 To find 30% of 95 kg 10% of 95 kg = 9.5 kg Multiply 9.5 by 3 to find 30% Answer is 28.5 kg. To find 40% of 1492 kg 10% of 1492 kg = 149.2 kg Multiply 149.2 by 4 to find 40% Answer is 596.8 kg. Construction Skills Queensland – Integrated LLN and Learning Support Strategy 4 Calculating in Construction - Percentages 5. Calculating 25%, 50% or 75% To find 25% of an amount 25% means one quarter, so divide by 4. For example, find 25% of $300 300 divided by 4 = $75 To find 50% of an amount 50% means one half, so divide by 2. For example, find 50% of $300 300 divided by 2 = $150 To find 75% of an amount 75% means three quarters, so divide by 4 and multiply by 3. For example, find 75% of $300 = 300 divided by 4 = 75 Then multiply 75 by 3 = $225 6. Other common percentages To find 33% of an amount 33 % means one third, so divide by 3. For example, find 33 % of $300 300 divided by 3 = $100 To find 5% of an amount 5% is half of 10% so find 10% and then divide by 2. For example, find 5% of $300 10% = $30 Divide by two to find 5%. Answer = $15 7. Learners complete Worksheet 2 with trainer support and answers. Construction Skills Queensland – Integrated LLN and Learning Support Strategy 5 Calculating in Construction - Percentages Worksheet 1 - Calculating Percentages Write these as percentages. Percentage 1. 15 out of 25 2. 9 out of 45 3. $14 out of $20 4. 5 km out of 20 km 5. 600 litres out of 900 litres 6. 45 m out of 60 m 7. 3 kg out of 40 kg 8. 250 mm out of 5 m. 9. 1200 m out of 4 km. 10. 30 cents out of $2.00. Construction Skills Queensland – Integrated LLN and Learning Support Strategy 6 Calculating in Construction - Percentages Worksheet 1 Answers Calculating Percentages Write these as percentages. Answer 1. 15 out of 25 60 % 2. 9 out of 45 20 % 3. $14 out of $20 70 % 4. 5 km out of 20 km 25 % 5. 600 litres out of 900 litres 66.67% 6. 45 m out of 60 m 75 % 7. 3 kg out of 40 kg 7.5 % 8. 250 mm out of 5 m. 5% 9. 1200 m out of 4 km. 30 % 10. 30 cents out of $2.00. 15 % Construction Skills Queensland – Integrated LLN and Learning Support Strategy 7 Calculating in Construction - Percentages Worksheet 2 – Common Percentages Using the strategies discussed for common percentages, calculate the answers to these. Percentage 1. 25% of 2 000 m 2. 20% of 4 000 mm 3. 10% of 628 kg 4. 50% of 18 tonnes 5. 40% of 70 workers 6. 75% of $56 7. 10% of 2 765 mm 8. 30% of 40kg 9. 33 % of 600 tonnes 10. 5% of 9 000 m Construction Skills Queensland – Integrated LLN and Learning Support Strategy 8 Calculating in Construction - Percentages Worksheet 2 – Common Percentages Answers Percentage 1. 25% out of 2 000 m 500 m 2. 20% of 4 000 mm 800 mm 3. 10% of 628 kg 62.8 kg 4. 50% of 18 tonnes 9 tonnes 5. 40% of 70 workers 28 workers 6. 75% of $56 $42 7. 10% of 2 765 mm 276.5 mm 8. 30% of 40kg 12 kg 9. 33 % of 600 tonnes 200 tonnes 10. 5% of 9 000 m 450 m Construction Skills Queensland – Integrated LLN and Learning Support Strategy 9

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