1) In a test cosisting of 20 multiple-choice, 5 marks will be given for a correct answer, 3 marks will be deducted for a wrong answer and no mark for unanswered question. If Simon answered 16 question in the test and got 56 marks, how many questions did Simon answer correctly?
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F.1 數學題
2012-06-28 2:20 am
回答 (2)
2012-06-28 2:39 am
✔ 最佳答案
1)Let n be the number of questions that Simon answered correctly.
Then, number of questions that Simon answered incorrectly = 16 - n
5n - 3(16 - n) = 56
5n - 48 + 3n = 56
8n = 104
n = 13
Ans: Simon answered 13 questions correctly.
參考: 胡雪
2012-06-28 3:18 am
Let X = no of correct answer, Y = no of wrong answer
X + Y = 16
X = 16 - Y
5X - 3Y = 56
5(16 -Y) - 3Y = 56
5(16 -Y) = 56 + 3Y
80 - 5Y = 56 + 3Y
80 - 56 = 3Y + 5Y
24 = 8Y
24/8 = Y
3 = Y
no of wrong answer = 3
5X - 3Y = 56
5X - 3*3 = 56
5X - 9 = 56
5X = 56 +9
5X = 65
X = 13
no of correct answer = 13
X + Y = 16
X = 16 - Y
5X - 3Y = 56
5(16 -Y) - 3Y = 56
5(16 -Y) = 56 + 3Y
80 - 5Y = 56 + 3Y
80 - 56 = 3Y + 5Y
24 = 8Y
24/8 = Y
3 = Y
no of wrong answer = 3
5X - 3Y = 56
5X - 3*3 = 56
5X - 9 = 56
5X = 56 +9
5X = 65
X = 13
no of correct answer = 13
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