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INTRODUCTION Many students worry about anything to do with numbers, having done little since their GCSEs. This booklet has been designed to offer practice and explanation in basic processes, particularly to anyone facing employers’ selection tests. It uses material developed by Clare Wright, Tom Frank, and Eric Williams of Birmingham University Careers Centre, where it has been successfully used for some time. Regaining numerical confidence can take a little while but, if you once had the basic skills, practice should bring them back. If, however, you encounter real problems perhaps you should question your motives. Employers don’t test you just to make life difficult. They do it because their jobs demand a particular level of proficiency. If you’re struggling to meet that level, or not enjoying it, is their job right for you? CONTENTS 1.Decimals ………………………………………………………………………………………………. page2 2.Fractions ……………………………………………………………………………………………… 5 3.Approximations …………………………………………………………………………………… 10 4.Averages ………………………………………………………………………………………………. 12 5.Percentages …………………………………………………………………………………………. 14 6.Ratios ……………………………………………………………………………………………………. 17 7. Answers ………………………………………………………………………………………………… 19 SECTION 1 - DECIMALS The most common use of decimals is probably in the cost of items. If you’ve worked in a shop or pub, you’re probably already familiar with working with decimals. Addition and Subtraction The key point with addition and subtraction is to line up the decimal points! Example 1 2.67 + 11.2 = 2.67 +11.20 ® in this case, it helps to write 11.2 as 11.20 13.87 Example 2 14.73 – 12.157 = 14.730 ® again adding this 0 helps - 12.157 2.573 Example 3 127.5 + 0.127 = 127.500 + 0.127 127.627 Multiplication When multiplying decimals, do the sum as if the decimal points were not there, and then calculate how many numbers were to the right of the decimal point in both the original numbers - next, place the decimal point in your answer so that there are this number of digits to the right of your decimal point. Example 4 2.1 x 1.2. Calculate 21 x 12 = 252. There is one number to the right of the decimal in each of the original numbers, making a total of two. We therefore place our decimal so that there are two digits to the right of the decimal point in our answer. Hence 2.1 x 1.2 =2.52. Always look at your answer to see if it is sensible. 2 x 1 = 2, so our answer should be close to 2 rather than 20 or 0.2 which could be the answers obtained by putting the decimal in the wrong place. Example 5 1.4 x 6 Calculate 14 x 6 = 84. There is one digit to the right of the decimal in our original numbers so our answer is 8.4 Check 1 x 6 = 6 so our answer should be closer to 6 than 60 or 0.6 （责任编辑：职场达人） |
