Direct and Inverse ProportionA selfmarking exercise in three levels on solving direct and inverse variation problems. 
This is level 1; Direct proportion. You can earn a trophy if you get at least 9 correct.
InstructionsTry your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help. When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file. 



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Level 1  Direct proportion
Level 2  Inverse proportion
Level 3  Mixed nonlinear questions
Unitary Method  Test your understanding of the Unitary Method for solving real life proportion problems with this online, selfmarking quiz.
Exam Style Questions  A collection of problems in the style of GCSE or IB/Alevel exam paper questions (worked solutions are available for Transum subscribers).
More on this topic including lesson Starters, visual aids, investigations and selfmarking exercises.
This video is from Mannel's Maths Music.
If \(a\) varies directly with \(b\) and \(a=24\) when \(b=8\) find \(a\) when \(b=9\)
$$a \propto b$$ $$a = kb$$Where \(k\) is some constant. If \(a=24\) when \(b=8\) then
$$24 = 8k$$ $$k = 3$$so the equation is
$$a = 3b$$If \(b = 9\) then
$$a = 3 \times 9 = 27$$If \(a\) is inversely proportional to \(b\) and \(a=4\) when \(b=6\) find \(a\) when \(b=8\)
$$a \propto \frac{1}{b}$$ $$a = \frac{k}{b}$$Where \(k\) is some constant. If \(a=4\) when \(b=6\) then
$$4 = \frac{k}{6}$$ $$k = 24$$so the equation is
$$a = \frac{24}{b}$$If \(b = 8\) then
$$a = 24 \div 8 = 3$$If \(a\) is directly proportional to the square of \(b\) and \(a=24\) when \(b=2\) find \(a\) when \(b=3\)
$$a \propto b^2$$ $$a = kb^2$$Where \(k\) is some constant. If \(a=24\) when \(b=2\) then
$$24 = 2^2 \times k$$ $$k = 6$$so the equation is
$$a = 6b^2$$If \(b = 3\) then
$$a = 6 \times 3^2 = 54$$Don't wait until you have finished the exercise before you click on the 'Check' button. Click it often as you work through the questions to see if you are answering them correctly. You can doubleclick the 'Check' button to make it float at the bottom of your screen.
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Claire Longmoor, Twitter
Monday, September 2, 2019