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一條中一數學題目(容易)請幫我!!!

發問:

2 times x is added to 100 and then the sum obtained is decreased by 30%.If the overall result is equal to increase x by 60%, find x 更新: 2. The marked price of an Mp3 player was $512. Ben bought is at a discount of 20% and sold it for the original marked price . What was his profit per cent ?

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1. 2 times X is added to 100 = 2X + 100 the sum obtained is decreased by 30% = (2X + 100) (1-30%) ... (1) increase X by 60% = X (1+60%) ... (2) thus, (1) = (2) (2X + 100) (1-30%) = X (1+60%) (2X + 100) (0.7) = X (1.6) 1.4X + 70 = 1.6X 70 = 1.6X - 1.4X 70 = 0.2X X = 350 2. marked price = 512 Ben bought = marked price x (1-discount in %) Ben bought = 512 x (1-20%) Ben bought = 409.6 Ben sold = 512 Ben's profit % = 100% x (512 - 409.6) / 409.6 Ben's profit % = 25%

其他解答:

(1) (2X + 100) * 70% = X * (1+60%) 1.4X + 70 = 1.6X 70 = 0.2X X = 70/0.2 X = 350 (2) (512 X 20%) / [512 X (1-20%) X 100% = 102.4 / 409.6 X 100% = 25%8758B59A7FA1EEA7