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mitaliisrani
- Senior | Next Rank: 100 Posts
- Posts: 56
- Joined: Sun Mar 21, 2010 11:06 am
If a,b, and c are positive, is ac>5?
1) a+b=3
2) 4=c-b
1. a + b = 3 , possible combinations:
(0.5 2.5) (1, 2) (2,1) --- (0,3) and (3,0) is ruled out because 0 is neither positive nor negative.
This statement does not say anything about c so ruled out
ac could be less than 5(1*2) or could be greater than 5 (1*6 )
2. c - b = 4
This statement is useless because all it tells us is that c is 4 ahead of b on the number line.
c,b could be 60, 56 or 3.99, 0.1
We are not told anything about A so Eliminate.
Combined.
a+b = 3
c-b = 4
add them
a + c = 7
minimum value of a or c could be 1, and if a is 1 can has to be 6 to satisfy the equation and ac would be greater than 5
but if a is 0.5 and b is 6.5 then ac would be 3.25, which is less than 5
Hence even together both equations do not help us in answering the question.
