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The ratio of television sets to radios at an electronic store before

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The ratio of television sets to radios at an electronic store before [#permalink]

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The ratio of television sets to radios at an electronic store before a new shipment arrives is 12:7. If no television sets or radios leave the store and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets
(2) The new shipment contains 77 radios

Kudos for a correct solution.
[Reveal] Spoiler: OA

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Re: The ratio of television sets to radios at an electronic store before [#permalink]

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Bunuel wrote:
The ratio of television sets to radios at an electronic store before a new shipment arrives is 12:7. If no television sets or radios leave the store and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets
(2) The new shipment contains 77 radios

Kudos for a correct solution.


Solution: Ratio = 12:7. Let x and y be no. of new TV sets and radios resp.
New ratio = 12k+x:7k+y which depends on x and y. We need both of them.

Statement1 : x = 132. Insufficient.

Statement2 : y = 77. Insufficient.

Combined : New ratio = 12k+132:7k+77 =12(k+11):7(k+11) = 12/7.Sufficient

Option C
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Re: The ratio of television sets to radios at an electronic store before [#permalink]

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Bunuel wrote:
The ratio of television sets to radios at an electronic store before a new shipment arrives is 12:7. If no television sets or radios leave the store and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets
(2) The new shipment contains 77 radios

Kudos for a correct solution.


(1) The new shipment contains 132 television sets-Clearly Insufficient
(2) The new shipment contains 77 radios-Clearly Insufficient

Let us take numbers. If there are 12 TV's and 7 radios, then new ratio=(12+132)/7+77=144/84=12/7
If there are 120 TV's and 70 radios, then new ration=252/147=12/7
Answer C
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Re: The ratio of television sets to radios at an electronic store before [#permalink]

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New post 17 Sep 2015, 08:30
Answer is C


using 1 and 2 we can get the value of the new ratio.
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Re: The ratio of television sets to radios at an electronic store before [#permalink]

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New post 20 Sep 2015, 22:12
Bunuel wrote:
The ratio of television sets to radios at an electronic store before a new shipment arrives is 12:7. If no television sets or radios leave the store and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets
(2) The new shipment contains 77 radios

Kudos for a correct solution.


VERITAS PREP OFFICIAL SOLUTION:

Here, the trap answer is E. Note that it’s “satisfying” for you to be able to recall about ratios that, when only given an initial ratio and then adding a particular number, you cannot tell the impact on the new ratio (were there 19 appliances to start, or 19,000?). You can pat yourself on the back for knowing that about ratios, feel confident in your answer, and move on. But you haven’t spotted the “sucker” — which is that there’s one exception: If the numbers that you add are in the same ratio as the original, the ratio remains unchanged. And 132 TVs and 77 radios added is a ratio of 12:7 (each is a multiple of 11). So the correct answer is C — we can prove with both statements together that the ratio remains at 12:7.

And here is where the “spot the sucker” mentality can help you — that the answer is C probably does not present itself too clearly to anyone based on the numbers. But if you know to suspect a trap, and choice E seems to come a bit too easy, you know that you should spend some time investigating further. A common Data Sufficiency trap is for the test to give you an answer that comes with a little bit of satisfaction (“I know that rule!”) but that still doesn’t take much time or ingenuity to solve. Know that low levels of satisfaction are highly correlated with trap answers — use that as your cue to investigate just a bit further.
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The ratio of television sets to radios at an electronics store before [#permalink]

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The ratio of television sets to radios at an electronics store before a new shipment arrives is 12:7. If no television sets or radios leave the store, and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets.
(2) The new shipment contains 77 radios.

Kudos for a correct solution.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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The ratio of television sets to radios at an electronics store before [#permalink]

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New post 29 Sep 2015, 05:51
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Bunuel wrote:
The ratio of television sets to radios at an electronics store before a new shipment arrives is 12:7. If no television sets or radios leave the store, and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets.
(2) The new shipment contains 77 radios.

Kudos for a correct solution.


(1) The new shipment contains 132 television sets.

We do not know about RADIO in new shipment => DONT KNOW the ratio of television sets to radios after the new shipment arrives => INSUF
(2) The new shipment contains 77 radios
Do not know TV in new shipment => INSUF

(1) + (2) The ratio of television sets to radios after the new shipment arrives = (12a+132)/(7a+77)=12(a+11)/7(a+11) = 12/7
SUFFICIENT

Ans: C
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Re: The ratio of television sets to radios at an electronics store before [#permalink]

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New post 29 Sep 2015, 14:18
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This is basically a trick question. In order to know the new ratio of TVs to radios, we'd like to know the total numbers. When we see that each statement gives us numbers for the new shipments, we certainly want to know both those numbers--neither statement by itself is going to be sufficient. However, it seems obvious that without knowing how many TVs and radios are in the store to begin with, we can't tell how the shipment affects the total. This would make E look like the answer.

However, if we look at the ratio of the new shipment, it's still 12 to 7. This is the ONE situation in which we can know the new ratio without knowing the original numbers. If the new shipment is in the exact same ratio as we had before, then the ratio is unchanged. Sneaky . . .
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Re: The ratio of television sets to radios at an electronics store before [#permalink]

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Bunuel wrote:
The ratio of television sets to radios at an electronics store before a new shipment arrives is 12:7. If no television sets or radios leave the store, and the only television sets and radios that arrive are in the new shipment, what is the ratio of television sets to radios after the new shipment arrives?

(1) The new shipment contains 132 television sets.
(2) The new shipment contains 77 radios.

Kudos for a correct solution.


This question is a caveat to blindly following the much hyped strategy of DS questions - if you can establish the sufficiency, do not solve the question.

There are cases where you need to look carefully before deciding whether the sufficiency condition is actually met. Some of them are:

1. Quadratic equations - Ensure that the roots are not the same. If they are the same, there could be a unique solution though you may not expect it.
2. Solving simultaneous equations - Ensure that the equations are not the same (e.g. one is a multiple of the other). There is no unique solution in this case.
3. Ratios - Ensure that the ratios are not the same. If they are, when you add them, the ratio stays the same.
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Re: The ratio of television sets to radios at an electronic store before [#permalink]

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