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f.1 maths help!!!!!(15)2題

發問:

1.There were n boys and n girls originally in a group of students.If 2 boys join the group and 40 girls leave the group ,then 60% of the new group will be boys. Find the value of n.(*男女人數本來是一樣的)2.A shop owner offers a 30% discount to customers . If the cost of an item is $6000 and a 405 profit to be made... 顯示更多 1.There were n boys and n girls originally in a group of students.If 2 boys join the group and 40 girls leave the group ,then 60% of the new group will be boys. Find the value of n. (*男女人數本來是一樣的) 2.A shop owner offers a 30% discount to customers . If the cost of an item is $6000 and a 405 profit to be made , how much should the marked price be? 更新: 2.A shop owner offers a 30% discount to customers . If the cost of an item is $6000 and a 40%profit to be made , how much should the marked price be? sorry !!!!我打錯了40%profit

最佳解答:

(1) Original numbers of boys are girls are both n. Later they become n + 2 and n - 40 respectively. The total is n + 2 + n - 40 = 2n - 38 The percentage of boys = (n + 2) / (2n - 38) * 100% = 60% n + 2 = (2n - 38) * 0.6 n + 2 = 1.2n - 22.8 24.8 = 0.2n n = 124 (2) Let the marked price be $x Selling price = $x * (1 - 30%) = $0.7x Profit = $0.7x - $6000 = $405 0.7x = 6405 x = 9150 The marked price should be $9150 2009-12-30 11:25:26 補充： (2) Let the marked price be $x Selling price = $x * (1 - 30%) = $0.7x Profit % = ($0.7x - $6000)/$6000 * 100% = 40% 0.7x - 6000 = 0.4 * 6000 0.7x = 8400 x = 12000 The marked price should be $12000

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