Please answer the question in steps and solution..
Peter answered 15 questions in a quiz and obtained 29 points. If he scored 3 points for each correct question and was deducted 1 ppoints for each wrong answer, how many question did peter answer correctly?
Math Problem! Fast ! 20 points
2011-01-06 3:52 am
回答 (2)
2011-01-06 4:03 am
✔ 最佳答案
Suppose he answered x questions correctly and y questions wrongly.x + y = 15-------------(1)
(3)x + (-1)y = 29
3x - y = 29------------(2)
(1) + (2), 4x = 44
x = 11
So he answered 11 questions correctly.
2011-01-06 17:27:13 補充：
x + y = 15
3x - y = 29 +
----------------------------------------
4x = 44
2011-01-06 17:28:43 補充：
sorry,上面顯示唔到。其實上面既做法係左邊+左邊 = 右邊+右邊,即係
x + y = 15
3x - y = 29
所以 (x + y) + (3x - y) = 15 + 29
4x = 44
x = 11
參考: 請勿抄襲
2011-01-06 5:57 am
Let the number of question that Peter answer correctly and wrongly be t and a respectively:
3t-a=29........(1)
t+a=15.........(2)
From (2)
t+a=15
a=15-t..........(3)
Sub. (3) into (1)
3t-a=29
3t-15+t=29
4t=44
t=11
Peter answer 11 question correctly.
3t-a=29........(1)
t+a=15.........(2)
From (2)
t+a=15
a=15-t..........(3)
Sub. (3) into (1)
3t-a=29
3t-15+t=29
4t=44
t=11
Peter answer 11 question correctly.
收錄日期: 2021-04-13 17:44:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110105000051KK00990