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Comment on Divisor of 86420
Hi just trying to assess how
This is a SUPER HARD question
This is a SUPER HARD question. It's definitely 750+
Hi Brent, if we consider any
We get 72/(6^-2) = 72/(1\36) = (72)(36)
This makes 6^-2 a divisor of 72, in the same way for the above ques we can consider any -ve value for n?
That's a great idea, but we
That's a great idea, but we can't say that 6^(-2) a divisor of 72.
Divisors must be INTEGERS, and 6^(-2) = 1/16 (which is not an integer)
Cheers,
Brent
Good question
I'm glad you like it :-)
I'm glad you like it :-)
Please let me know if this is
2 x 2 x 5 x 11 x 17 x 23
By recognizing there is no 3 in the prime factorization, i concluded 6 (nor any multiple of 6 i.e 6^n) is not a divisor of 86420, meaning n must equal 0, knowing that the question is not flawed. by assuming n is 0, i solved and got 1.
That approach is perfect (yet
That approach is perfect (yet time consuming).
minor point: Although the approach is 100% valid, your prime factorization is a little off.
86,420 = 2 x 2 x 5 x 29 x 149 (still no 3's! ;-)
Cheers,
Brent
Hi Brent,
I solved this using the following logic:
86420 = 8 + 6 + 4 + 2 + 0 = 20.
A number divisible by 6 should have the sum of its digits divisible by 3 and be even. 86420 is even but its digits do not add up to be number divisible by 3.
The only way 6^n can be divisible is if n = 0, in which case 2^n - n^2 = 1
Hence, B
Took me less than 1.5 minutes :)
Perfect solution - nice work
Perfect solution - nice work Karaan!
Thanks Brent for the
Given the computer adaptive
Given the computer adaptive nature of the GMAT, practically all test takers will see questions they have no idea how to solve.
When this happens, consider the following options:
- test the answer choices
- test values and look for a pattern
- examine at simpler (but similar) question
Above all else, don't waste 5 minutes on a question if you have no idea where to even start
Noted thanks Brent.