inequality trap

[maihuna]

If a + b > – c, is a > 2?

(1) a + b + c > 8
(2) – a + b + c < – 4

[cramya]

I am getting B)

Given : a+b > -c
a+b+c>0

Find: Is a > 2?

Stmt I

a+b+c > 8

a=-10000 b=2000000 c=300000000

a>2 no

a=5 b=1 c=3 a+b+c>8 a>2 YES

INSUFF

Stmt II

a+b+c>0


– a + b + c < – 4

b+c+4<a

b+c < a-4 i.e a-4 > b+c ( I )

a+b+c>0
a> -b-c ( II )

Add I and II

2a-4>0
2a > 4
a>2

SUFF
Choose B)

[maihuna]

B is OA. thanks

[adilka]

Given: a + b > – c
Stmt II: – a + b + c < – 4

Rearrange given as a+b+c>0 and then substract Stmt II from it

2a>4
a>2

[cramya]

Stmt II: – a + b + c < – 4

Rearrange given as a+b+c>0 and then substract Stmt II from it

2a>4
a>2

I know we can add inequalities facing same direction without affecting the combined inequality.

It comes out what we need to find but not sure if u can subtract inequalities facing different directio?

Thoughts anyone?

Regards,
CR

[ronniecoleman]

IMO B


A+ B+ C > 0

B+ C > -A ------1


B+ C+ 4 < A

Replace B+ C by -A

-A+ 4 < A

A > 2

[logitech]

Stmt II: – a + b + c < – 4

Rearrange given as a+b+c>0 and then substract Stmt II from it

2a>4
a>2

I know we can add inequalities facing same direction without affecting the combined inequality.

It comes out what we need to find but not sure if u can subtract inequalities facing different directio?

Thoughts anyone?

Cramya never ever perform an operation when the INEQS are facing different directions.

But if they are facing the same directions..I STILL WILL BE VERY CAREFUL!

-(-a) = +a

Regards,
CR

[adilka]

Stmt II: – a + b + c < – 4

Rearrange given as a+b+c>0 and then substract Stmt II from it

2a>4
a>2

I know we can add inequalities facing same direction without affecting the combined inequality.
It comes out what we need to find but not sure if u can subtract inequalities facing different directio?
Thoughts anyone?
Regards,
CR

Here is how it works:

Given: a+b+c>0
Stmt II: – a + b + c < – 4 can be rearranged as a-b-c>4 (basically, multiply by -1)
Hence:
a+b+c>0
a-b-c>4

add them together, you get 2a>4

[Ian Stewart]

Stmt II: – a + b + c < – 4

Rearrange given as a+b+c>0 and then substract Stmt II from it

2a>4
a>2

I know we can add inequalities facing same direction without affecting the combined inequality.

It comes out what we need to find but not sure if u can subtract inequalities facing different directio?

Thoughts anyone?

Regards,
CR

Yes, but when you subtract inequalities that face in opposite directions, you're really just doing the following:

-multiplying one of the inequalities by -1 on both sides, *reversing* the inequality (so they now face in the same direction);

-adding the two inequalities together.

I've never bothered to learn rules for subtracting inequalities, and I always do the steps above; it's the only way I feel confident about each step.

[cramya]

Thanks Ian and Adilka for the clarification.

[aj5105]

very cool..

I am getting B)

Given : a+b > -c
a+b+c>0

Find: Is a > 2?

Stmt I

a+b+c > 8

a=-10000 b=2000000 c=300000000

a>2 no

a=5 b=1 c=3 a+b+c>8 a>2 YES

INSUFF

Stmt II

a+b+c>0


– a + b + c < – 4

b+c+4<a

b+c < a-4 i.e a-4 > b+c ( I )

a+b+c>0
a> -b-c ( II )

Add I and II

2a-4>0
2a > 4
a>2

SUFF
Choose B)