F.3 Mathe questions

你好～～～

以下都是敝人的一些意見而已，如有錯誤請多多指教！

1. The priices of a moyuse-pad and a file-jacket are $35 and $48 respectively. Mr Lee wants to use $400 or less to buy 10 of them in total and as many
file-jackets as possible. How many mouse-pads should he buy?

Solution:

Let the mouse-pads he should buy be y.

Then, the number of file-jacket he should buy is (10 - y).

35y + 48(10 - y) <= 400

35y + 480 - 48y <=400

-13y <= 400 - 480

-13y <= -80

y >= 80 / 13

80 / 13 = 6.153846.......

Because the number of y must be an integer.

So, he should buy 7 mouse-pads.

希望可以幫到你～～～～～

2010-09-14 20:05:02 補充：
Yes, the one that Ken said is the alternative one.

Let x be the numbers of file-jackets that he can buy:
48x+35(10-x)<=400
48x+350-35x..<=400
13x................<=50
x.....................<=50/13----------------(He can buy 3 file jackets)
__________________
10-3
=7-------------(He can buys 7 mouse-pad)