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16 Sep 2014, 00:27
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What is the sum of \(a\), \(b\), and \(c\)?
(1) \(a:b:c = 3:4:7\)
(2) \(c - a = 12\)
(1) \(a:b:c = 3:4:7\)
(2) \(c - a = 12\)
17 Jul 2015, 00:49
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Official Solution:
What is the sum of \(a\), \(b\), and \(c\)?
(1) \(a:b:c = 3:4:7\)
The ratio by itself doesn't give the actual numerical values of \(a\), \(b\), and \(c\), so we cannot determine their sum. Not sufficient.
(2) \(c - a = 12\)
This statement by itself is clearly insufficient.
(1)+(2) From (1) we have that \(a:b:c = 3x:4x:7x\) for some number \(x\). Hence, from (2) we'd have that \(7x - 3x = 12\), which leads to \(x = 3\). Therefore, \(a + b + c = 3x + 4x + 7x = 14x = 42\). Sufficient.
Answer: C
What is the sum of \(a\), \(b\), and \(c\)?
(1) \(a:b:c = 3:4:7\)
The ratio by itself doesn't give the actual numerical values of \(a\), \(b\), and \(c\), so we cannot determine their sum. Not sufficient.
(2) \(c - a = 12\)
This statement by itself is clearly insufficient.
(1)+(2) From (1) we have that \(a:b:c = 3x:4x:7x\) for some number \(x\). Hence, from (2) we'd have that \(7x - 3x = 12\), which leads to \(x = 3\). Therefore, \(a + b + c = 3x + 4x + 7x = 14x = 42\). Sufficient.
Answer: C
General Discussion
02 Nov 2015, 12:46
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It is a very good question even when it is sub 600 but with permission I would like to add some strategies in data sufficiency regarding ratios and sums
operations
If you are given relations but no direct number then it is insufficient to know what is the addition, product or subtraction as ax bx and cx can be múltiples of x.
Hence always look at the statements separately and think about what the other statement is doing and why it is there. Those kind of subtleties hinge important hints to understand and crack advanced questions
Lastly, in ratios like this problem, remember that you need to homogenize the ratios in one single representative as Bunuell did and you need another piece of information that relates to ACTUAL QUANTITIES.
Remember to treat ratios as múltiples and think about quantity relations to crack the common factor
Thanks
operations
If you are given relations but no direct number then it is insufficient to know what is the addition, product or subtraction as ax bx and cx can be múltiples of x.
Hence always look at the statements separately and think about what the other statement is doing and why it is there. Those kind of subtleties hinge important hints to understand and crack advanced questions
Lastly, in ratios like this problem, remember that you need to homogenize the ratios in one single representative as Bunuell did and you need another piece of information that relates to ACTUAL QUANTITIES.
Remember to treat ratios as múltiples and think about quantity relations to crack the common factor
Thanks
