f.1 maths help!!!!!(15)2題

2009-12-30 6:52 pm

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1:

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

回答 (2)

用戶9112

2009-12-30 7:05 pm

✔ 最佳答案

(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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[匿名]

2009-12-31 12:44 am

這裏可以幫到你
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