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Math homework ;;help (下part)
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4. When a number is increased by 32% and then multiplied by 80%, the result is 1.9008. Find the number.5. Adding 28 to 3 times of a number is equal to 12 added to 5 times the number. Find the number.6. Mr Chan had a sum of money. He firrst used 40% of it and then used 30% of the rest .He... 顯示更多 4. When a number is increased by 32% and then multiplied by 80%, the result is 1.9008. Find the number. 5. Adding 28 to 3 times of a number is equal to 12 added to 5 times the number. Find the number. 6. Mr Chan had a sum of money. He firrst used 40% of it and then used 30% of the rest . He then had $ 210 left.How much did he have originally? 7. In a zoo there are 28 animals with 68 feet .If there are only hens and dogs , find the number of dogs. 幫下我啦!-3-
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4.) Let x be the number. x (1+32%) 80% = 1.9008 x 1.32 0.8 = 1.9008 x 1.056 = 1.9008 x = 1.8 The number is 1.8. 5.) Let y be the number. 28 + 3y = 12 + 5y 16 = 2y 2y = 16 y = 8 The number is 8. 6.) Let z be the money he had orginally. z (1-40%) (1-30%) = 210 z 0.6 0.7 = 210 z 0.42 = 210 z = 500 Mr Chan originally had $500. 7.) Let a be the number of dogs and b be the number of hens. a + b = 28 --- (1) 4a + 2b = 68 --- (2) From (1), b = 28 - a --- (3) Put (3) into (2), 4a + 2(28 - a) = 68 4a + 56 - 2a = 68 2a = 12 a = 6 There are 6 dogs. 幫望幫到你 =]
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