Lesson: QC Strategy - Plugging in Numbers

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greenlight-admin's picture

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Is there any time when plugging in numbers is better than matching operations? Because it seems as if plugging in numbers is more cumbersome and is rather a way to check your answer when you have first used the faster/more efficient matching operations
greenlight-admin's picture

Sometimes the Plugging in Numbers is the approach when you can't see how to apply the other approaches.
That said, if there are several complicated operations involved, sometimes it's faster to plug in some "easy values" (e.g., 0, 1, -1, etc) to see if you can reach a solution faster.

Just wondering... Is it a more foolproof and robust approach to plug in two integers with the same absolute value but with opposite signs (e.g., +1 and -1) to check for symmetry? I was thinking of always using +1 and -1. If they give me different results, then I know the answer is D. If they give me the same results, then try 0, just to be sure. Would you say this is a dominant strategy for this type of problem?
greenlight-admin's picture

That's a good strategy.

Of course, if you get the same outcome with 1, -1 and 0, try 1/2, -1/2, 10 and -10, to see if you get a different outcome.

As mentioned in the video, plugging in numbers has its limitations since you will never by 100% certain of your answer UNLESS you're lucky enough to get two different outcomes (which means the correct answer is D).

Sir for this quantity just plug in 1&-1 we will get the correct answer just plug in any number with its opposite value.
E.g. 1&-1,10&-10,1/2&-1/2 with 0 with all to confirm our answer
greenlight-admin's picture

You're referring to the question that begins at 0:10. Yes, plugging in those two values will work for that question to determine that the correct answer is D.

Thank you sir

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