Tim participates in a competition.It is known that each participant has to answer x questions , where 30 marks will be obtained for each correct answer,20 marks will be drducted for each wrong answer and 0 mark for no answer. Tim answer 3/8 of the questions correctly and gives up 8 questions.
a)Express the number of questions Tim answers wrongly in terms of x.
b)If Tim opbtain 130 marks,find the value of x.
Maths
2007-12-19 4:41 am
回答 (2)
2007-12-19 5:17 am
✔ 最佳答案
a) let the no.of questions Tim answers wrongly be y y = x-8 - 3/8x = 5/8x-8
(因佢答中左全部question既3/8, 所以有3/8x既question答中,只張x(total no. of qusetion) 減番佢岩左幾條同埋佢放棄左幾多條,就知佢答錯左幾多條)
b) -20(5/8x-8) + 30(3/8x) + 8(0) = 130 (個20要加負,因為佢俾人扣20分,之後times番d分數)
(-100/8)x + (90/8)x +160 = 130
-10x/8 = -30
-10x = -240
x = 24
希望幫到你啦!
參考: me
2007-12-19 5:57 am
a) the number of questions Tim answers wrongly :
=X-(3/8)X-8
=(5/8)X-8
b) the value of x :
30(3/8)X-20[X-(3/8)X-8]=130
(90/8)X-20[(5/8)X-8]=130
(90/8)X-(100/8)X+160=130
(90/8)X-(100/8)X=-30
-10X=-240
X=24
20年無計過數,希望無做錯喇. GOOD LUCK!
2007-12-18 22:01:18 補充：
O, SORRY原來已有高人指路,甘拜下風....
=X-(3/8)X-8
=(5/8)X-8
b) the value of x :
30(3/8)X-20[X-(3/8)X-8]=130
(90/8)X-20[(5/8)X-8]=130
(90/8)X-(100/8)X+160=130
(90/8)X-(100/8)X=-30
-10X=-240
X=24
20年無計過數,希望無做錯喇. GOOD LUCK!
2007-12-18 22:01:18 補充：
O, SORRY原來已有高人指路,甘拜下風....
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https://hk.answers.yahoo.com/question/index?qid=20071218000051KK03329