Lesson: Guessing Strategies

Comment on Guessing Strategies

Brent, would it be legit to assume that since the compliment here is 0.7 and we look for it to occur 3 time (No tails) then one of the distractions would be an answer choice that ends with 3 (7 to the power of 3)? also - the correct answer choice must end with 7 (1-something ends with 3). in this example, this would have left us with 2 options and then using number orientation and sizing - we are down to one answer. WDYT?
gmat-admin's picture

That strategy makes total sense.

This lesson is primarily about what to do if you're totally lost, and how to use your gut instincts to eliminate answer choices before guessing.

That said, your approach would allow us to eliminate B, D and E

Awesome approach - totally worth !

Dear Brent,
Thank you so much for these video lessons! I have actually started to enjoy studying for the GMAT because of you :)
gmat-admin's picture

I'm delighted to hear that - thanks!

Same for me. I hated GMAT study until I found Brent. The only thing that would make me not study now is other commitments but not the boredom that I used to associate with GMAT prep.
gmat-admin's picture

Very nice of you to say - thanks!

Dear Brent ,Thanks for the amazing videos ..
Its really helpful to me Every thing is properly planned in a systematic way ..
Really appreciate your efforts ..
May god bless u with more blessings ..

I have one query , just want to know that is this much math resources and questions you posted along with videos are enough to score 49 or 50 in maths or if no they what additions i should follow then ..?

Thanks in advance :)
gmat-admin's picture

Thanks for the kind words about my course!
The answer to your question is yes, the video lessons and practice questions in this course cover everything you need to get a top score in quant (and in verbal)


Hi Brent!

What is the solution to this question?
How would we go about solving it (guessing aside)?

Thank you in advance.

gmat-admin's picture

One approach is to use the complement.

= 1 - P(all 3 tosses are heads)
P(all 3 tosses are heads) = P(1st toss is heads AND 2nd toss is heads AND 3rd toss is heads)
= P(1st toss is heads) x P(2nd toss is heads) x P(3rd toss is heads)
= 0.7 x 0.7 x 0.7
= 0.343
So, P(at least 1 tails) = 1 - 0.343 = 0.657


Hi Brent,

While I was able to arrive on the correct answer, I was not sure on how to use the info. that the coin is "unfair".
Please shed some light on the same.

Warm Regards,
gmat-admin's picture

A "fair" coin is a coin that has a 50% chance of turning up heads, and a 50% chance of turning up tails.

In other words, P(getting HEADS) = P(getting TAILS) = 0.5

For this question, we're told P(getting TAILS) = 0.3, which means P(getting HEADS) = 0.7
As such, this coin is considered "unfair"

Does that help?


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