F.1 mAthz 4題數__

babe.3.

2009-07-18 6:31 am

1. x/2+2x/3=3x/4-1/12 [[分數黎的:D
2. Mr Choi is 15 years older than his sister. Five years later, he will be twice as old as his sister. Find their present ages.
3. A cake is shared between Joseph and David. Joseph gets three quarters of the cake, and David gets the rest. If Joseph gives 100g of his share of cake to David, then Joseph will have twice as much as David. Find the weight of the cake.
4. In a test consisting of 20 multiple-choice questions, 5 marks will be given for a correct answer, 3 marks will be deducted for a wrong anwer and on marks for unanswered questions. If Simon answered 16 questions in the test and got 56 marks, how many questions did Simon answer correctly?

系d英文多左d-3-
要有步驟..同埋系方程;]]
吾該晒呀各位>_<

回答 (1)

用戶7639

2009-07-18 6:58 am

✔ 最佳答案

圖片參考：http://h.imagehost.org/0452/ScreenHunter_03_Jul_17_22_55.gif

2.Let the ages of Mr Choi be x,then the ages of his sister be x-15.
x+5=2[(x-15)+5]
x+5=2(x-10)
x+5=2x-20
x=25
∴their present ages are 25 and 10.

3.Let the weight of the cake be y g.
3/4y – 100=2(1/4y + 100)
3/4y-100=1/2y+200
3/4y - 1/2y=300
1/4y=300
y=1200
∴the weight of the cake be 1200 g.

4.Let the number of correct answers be x,then the number of wrong answers be 16-x.
5x-3(16-x)=56
5x-48+3x=56
8x=104
x=13
∴the number of correct answers=13

圖片的超連結
http://h.imagehost.org/0452/ScreenHunter_03_Jul_17_22_55.gif

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