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.
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(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

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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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.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

(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

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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