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17 Mar 2025, 09:01
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Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
25% (01:24) correct
75% (02:04) wrong based on 8 sessions
History
Date
Time
Result
Not Attempted Yet
If \(12a + 3b = 1\) and \(7b – 2a = 9,\) what is the average (arithmetic mean) of a and b?
A. 0.1
B. 0.5
C. 1
D. 2.5
E. 5
A. 0.1
B. 0.5
C. 1
D. 2.5
E. 5
17 Mar 2025, 09:30
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12a+3b=1.......... (1)
-2a+7b=9.......... (2)
Multiply equation (2) by 6 and add the equations
12a+3b=1
-12a+42b=54
————————
45b=55
b=55/45
And -2a=9-7(11/9) ....... a= -2/9
(a+b)/2= ((-2/9)+(11/9))/2=0.5
Answer: B
-2a+7b=9.......... (2)
Multiply equation (2) by 6 and add the equations
12a+3b=1
-12a+42b=54
————————
45b=55
b=55/45
And -2a=9-7(11/9) ....... a= -2/9
(a+b)/2= ((-2/9)+(11/9))/2=0.5
Answer: B
23 Mar 2025, 11:06
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OE
Add the two equations:
Do not waste time solving for a and b.
Answer: B
GMAT-Club-Forum-7d3oxhak.png [ 30.15 KiB | Viewed 448 times ]
Add the two equations:
Do not waste time solving for a and b.
Answer: B
Attachment:
GMAT-Club-Forum-7d3oxhak.png [ 30.15 KiB | Viewed 448 times ]
