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F3 Percentage question唔該幫幫手 快入來答!!!

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An alloy A contains 35% of zinc by weight.Some alloy A and pure zinc are melted to form a new alloy that weights 400 kg and contains 66又16分之1 % of zinc.What are the weights of alloy A and zinc needed respectively to form the new alloy?(give the answers correct to the nearest kg)Answer: alloy A: 209 kg, zinc:... 顯示更多 An alloy A contains 35% of zinc by weight. Some alloy A and pure zinc are melted to form a new alloy that weights 400 kg and contains 66又16分之1 % of zinc. What are the weights of alloy A and zinc needed respectively to form the new alloy? (give the answers correct to the nearest kg) Answer: alloy A: 209 kg, zinc: 191 kg Show me the steps please. THX!!!

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Let weight of alloy A neded be x Then weight of zinc needed = 400 - x Weight of Zinc in alloy A is 0.35x The % of zinc in New alloy is than (400 - x + 0.35x) / 400 = [66 + 1 / 16] % => x = 208.85 or 209 and weight of zinc = 400 - 209 = 191

其他解答:

Let the weight of alloy A and pure zinc used by A kg and Z kg respectively Consider the new alloy, weight of zinc = 400 x (66 又16分1 %)kg =264.25kg Consider A, weight of zinc =A x 35% kg =0.35A kg Therefore, 0.35A + Z = 264.25 ...... (1) Besides, the sum of weights of Alloy A and Pure zinc should be equal to the weight of the new alloy A + Z = 400 ...... (2) (2) - (1) gives A - 0.35A = 400 - 264.25 0.65A = 135.75 A = 208.84615 (to 5 decimal place) i.e. weight of alloy A is 209kg (to the nearest kg) substitute A=209 into (2) 208.84615 + Z = 400 Z = 191.15 (to 2 decimal place) i.e. weight of pure zinc is 191kg (to the nearest kg)0D7DAC4E7B8CAAC5