問1題數學題~

First, let X be the number of questions she answer correctly
and Y be the number of questions she answer incorrectly
4X - 3Y > 2
X + Y = 30
if X = 10 ...Y = 20
she will get -20
here, we can know that if X increase 1,
her marks will increase 7
so that we can realize that X = 13 , Y = 17
4 (13) - 3 (17) = 1
here she get 1 mark,
so we should add 1 to X again
so that to fit the condition (she gets higher than 2 marks)
SO we can get
X = 14....Y = 16
The greatest number of question she answered incorrectly is 16

2007-05-02 17:58:54 補充：
我呢個方法係從思考方面去搵答案...樓上嗰位係用純數去計...樓主如果個功課係要show steps...用上面嗰一個is better

Let x be the number of incorrect answers, and so number of correct answers is 30-x

Scores she got
= 4*(30-x) - 3x
= 120-7x

If 120-7x >or= 2,
118 >or= 7x
x <or= 16.86

So the greatest number of questions she answered incorrectly is 16.

I not no you say what.