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heshamelaziry
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Statement 1:heshamelaziry wrote:Is a + b > 0?
1. 7a - b > 0
2. b - 6a > 0
[spoiler]How C is the answer ?[/spoiler]
7a - b > 0
7a > b
So, 7 a's are bigger than 1 b, but we don't know their positive/negative status. Insufficient.
Statement 2: Similar reasoning. Insufficient.
Combo:
When the inequality arrows are pointing in the same direction, you can stack the inequalities, and add them:
7a - b > 0
b - 6a > 0;
...rearranging
7a - b > 0
-6a +b > 0
_____________
a > 0 (adding the two inequalities)
So, a is positive. The second statement tells us:
b > 6a
If a is pos, and b is bigger than "a" (bigger than six of them), then of course, b is also positive.
Because both a and b are positive, their sum is positive.
The statements, although independently insufficient, are sufficient in combination.
Choose C.
