Thanks a lot guys, I find all your videos very well structured and thoughtful, they give us a lot of information in a very short time. They really helped me in forming my solution methods to different types of questions! Alex is a great tutor btw! Made things really easy to understand. :)
Hey Why isnt the Plugging in approach work in Q4, I assumed p= 8, q=16 and r=4 I am getting both B and D as correct. I am not able to figure out where I am going wrong...
also in 39.36 why does 3 need to go in both? isn't 21/3 = 7 which eventually is an integer? I know I am messing up somewhere on similar lines and hence would like your help Sir!
@@anushridicholkar2961 Let's deal with your second question first. Around 39:36, Alex says that 3 does NOT need to go into both. As long as it goes into one of the numbers in the numerator, we'll get an integer at the end. The bigger question is about using the "plugging in approach". You haven't done anything wrong, since the numbers you've used give integers when you plug them into (B) and (D). The issue comes in the wording of the question: "which of the following MUST be an integer?" You've shown that the expressions in both (B) and (D) will be an integer for the numbers you're using, so we can say they COULD be an integer, but we haven't done enough to say that either of them MUST be an integer. If we assumed p = 6, q = 12, and r = 3, answer choice (B) gives (12 + 6) / 3 = 18/3 = 6 but (D) gives (6*3)/12 = 18/12 = 3/2. This means we can rule out (D), and (B) is the answer to this question. This is why we suggest you stick to an algebraic method whenever you can. When we choose some numbers to plug into the options, it's hard to be completely sure that these numbers will work all the way through the question. If we think through the algebra in the way Alex does in the video, we can be sure that (B) is the right answer her without running into any problems with the numbers we've chosen. I hope that helps!
Good question! We get 36 because that's the "least common multiple" of 12 and 18. As you point out, the greatest common factor of 12 and 18 is 6. But the smallest number that 12 and 18 both go into (i.e. the "least common multiple" or LCM) is 36. Let me know if that helps!
hello, is it okay for me to not follow the order while watching this quant playlist? I mean i am studying topic wise and currently got some weakness in number theory so is it okay for me to watch only this video and not the ones that came before like exponents algebra etc?
Absolutely! You can think of our video series as a buffet -- go ahead and review the ones that grab your interest, and feel free to skip ones if you're already comfortable with the concepts.
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Thanks a lot guys, I find all your videos very well structured and thoughtful, they give us a lot of information in a very short time. They really helped me in forming my solution methods to different types of questions!
Alex is a great tutor btw! Made things really easy to understand. :)
solving more questions like the last one, thanks a lot team
thanks a lot for this series of gmat basics! very helpful and necessary for me
That's great to hear -- so glad you found the video helpful!!
Hey Why isnt the Plugging in approach work in Q4, I assumed p= 8, q=16 and r=4 I am getting both B and D as correct. I am not able to figure out where I am going wrong...
also in 39.36 why does 3 need to go in both? isn't 21/3 = 7 which eventually is an integer? I know I am messing up somewhere on similar lines and hence would like your help Sir!
@@anushridicholkar2961 Let's deal with your second question first. Around 39:36, Alex says that 3 does NOT need to go into both. As long as it goes into one of the numbers in the numerator, we'll get an integer at the end.
The bigger question is about using the "plugging in approach". You haven't done anything wrong, since the numbers you've used give integers when you plug them into (B) and (D). The issue comes in the wording of the question: "which of the following MUST be an integer?" You've shown that the expressions in both (B) and (D) will be an integer for the numbers you're using, so we can say they COULD be an integer, but we haven't done enough to say that either of them MUST be an integer.
If we assumed p = 6, q = 12, and r = 3, answer choice (B) gives (12 + 6) / 3 = 18/3 = 6 but (D) gives (6*3)/12 = 18/12 = 3/2. This means we can rule out (D), and (B) is the answer to this question.
This is why we suggest you stick to an algebraic method whenever you can. When we choose some numbers to plug into the options, it's hard to be completely sure that these numbers will work all the way through the question. If we think through the algebra in the way Alex does in the video, we can be sure that (B) is the right answer her without running into any problems with the numbers we've chosen.
I hope that helps!
11:51 sorry, how did the 6 turn into 36 again? because there are two numbers (12 and 18), therefore, 6 x 6?
Good question! We get 36 because that's the "least common multiple" of 12 and 18. As you point out, the greatest common factor of 12 and 18 is 6. But the smallest number that 12 and 18 both go into (i.e. the "least common multiple" or LCM) is 36.
Let me know if that helps!
@@GMATNinjaTutoring oh okay okay i see! yes that makes sense, thank you
hello, is it okay for me to not follow the order while watching this quant playlist? I mean i am studying topic wise and currently got some weakness in number theory so is it okay for me to watch only this video and not the ones that came before like exponents algebra etc?
Absolutely! You can think of our video series as a buffet -- go ahead and review the ones that grab your interest, and feel free to skip ones if you're already comfortable with the concepts.