We must DIVIDE BACK to find the ...



. Increase by a Percentage .What is best?Increase $375 by 20% or $360 by 26% Increase an amount by 28% 100% + 28% = 128%So it's the same as 128% of the amount.Multiply by 1.28 INCLUDEPICTURE "C:\\..\\..\\..\\..\\working\\Websites\\MR\\MR_website\\Year_10\\y10_Number\\images_percentages\\Y11_5_3.gif" \* MERGEFORMAT KEY: What is the % of? 100% + % increase. Increase by a Percentages Examples .QuestionWorkingAnswerIncrease $520 by 28% $520 x 1.28 = $Remember the 'shift =' for the % calculator function Calculator use:520 x 28 % + ????Increase $8.40 by 65% $8.40 x 1.65 = $?Calculator use:8.4 x 65 % + ?1) Increase $460 by 14%2) Add 26% onto $38.40. Decrease by a Percentage .What is best?$420 less 26% or $375 less 12%Decrease an amount by 28% 100% - 28% = 72%So it's the same as 72% of the amount.Multiply by 0.72 INCLUDEPICTURE "C:\\..\\..\\..\\..\\working\\Websites\\MR\\MR_website\\Year_10\\y10_Number\\images_percentages\\Y11_5_4.gif" \* MERGEFORMAT KEY: What is the % of? 100% – % increase. Decrease by a Percentage .QuestionWorkingAnswerDecrease $520 by 28% $520 x 0.72 = $145.60Remember the 'shift =' for the % calculator function Calculator use:520 x 28 % - ????Decrease $8.40 by 65% $8.40 x 0.55 = $2.94?Calculator use:8.4 x 55 % - ?1) Decrease $280 by 45%2) Decrease $22.40 by 16%3) A cow is on sale for 15% off. It normally costs $680. How much does it sell for?. Finding original after % increase (decrease) .Increasing by 10% then decreasing by 10% does NOT get back to the originalThe percentages are on different amounts eg Increase $400 by 10% $400 x 1.1 = $440 The 10% is on the $400 = $40 We add on $40 Now decrease $440 by 10% $440 x 0.9 = $396 NOT back to $400! The 10% is on the $440 = $44 We take off $44 ?We must DIVIDE BACK to find the original amount. Extension: Finding original after % increase (decrease) .Increase an amount by 28% 100% + 28% = 128%So it's the same as 128% of the amount.Multiply by 1.28 to get the new amountDIVIDE by 1.28 to get the ORIGINAL amount INCLUDEPICTURE "C:\\..\\..\\..\\..\\working\\Websites\\MR\\MR_website\\Year_10\\y10_Number\\images_percentages\\Y11_5_5.gif" \* MERGEFORMAT QuestionWorkingAnswerA shirt was increased by 28% and it now costs $56What was the original cost? $original x 1.28 = $56So $56 ÷ 1.28 = $43.75. Finding original after % increase (decrease) .Decrease an amount by 28% 100% - 28% = 72%So it's the same as 72% of the amount.Multiply by 0.72 to get the new amountDIVIDE by 0.72 to get the ORIGINAL amount INCLUDEPICTURE "C:\\..\\..\\..\\..\\working\\Websites\\MR\\MR_website\\Year_10\\y10_Number\\images_percentages\\Y11_5_6.gif" \* MERGEFORMAT QuestionWorkingAnswerA shirt was decreased by 28% and it now costs $34What was the original cost? $original x 0.72 = $34So $34 ÷ 0.72 = $47.22 ................
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