Sids wrote:

1. Q. can be answered using statement 1 alone.

2. Q. can be answered using statement 2 alone.

3. Statement 1 & 2 both are needed to answer the Q.

4. Q. can’t be answered even using both the statements

Q. Given that, X and Y are non negative. What is the value of X?

1. 2X+2Y <=40

2. X-2Y>=20

a) 1 b) 2 c) 3 d) 4

I have conflict of answer.

This is how I deal with this question:

If I am to get a value of X from 2 inequalities, I will get it from the border conditions. So more than anything, I will focus on the 'equal to' sign.

It is clear that either one of the inequalities will not give me the value of X. I have to see whether both together give me a value.

1. X + Y <= 20

2. X - 2Y >= 20

When Y is added to X, it is LESS than or equal to 20. When twice of Y is subtracted from X, it is GREATER than or equal to 20! Since Y cannot be negative, it must be 0 to give 20 in both cases. That is the only way in which both these conditions can be met. Hence, X must be 20.

fluke: Of course, your solution is absolutely correct and spot on. I am giving this method only to encourage you guys to think in terms of the 'big picture'. Very often, it helps you logically deduce your answer without much mathematical work.

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Karishma

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