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anonymousegmat
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Powerprep PS Grids 23 Jun 2007, 14:04
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can anyone explain how to answer this two questions quickly?



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AugiTh
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Powerprep PS Grids 24 Jun 2007, 11:38
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pp9.jpg....

I think 25 is wrong....just count all the squares above or below the diagonal squares. The ans is 15.

For the second question, i think there is no other way other than trying all the combinations. It would help to uniquely identify every junction uniquely (numbers or alphabets) so as to avoid a retrace!
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KillerSquirrel
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Powerprep PS Grids 24 Jun 2007, 13:40
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For the first problem:

(n*n-n)/2 =

(6*6-6)/2 = 15

:-D
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ian7777
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Powerprep PS Grids 24 Jun 2007, 13:45
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For the first one, once you see the patter, you see that there are five boxes in the top row, then 4, then 3, etc. You should learn how to add consecutive numbers quickly:

It's always the middle number times the number of numbers.

So that's 3 (the middle) times 5 (the number of numbers), which is 15.
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anonymousegmat
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Powerprep PS Grids 24 Jun 2007, 21:41
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AugiTh
pp9.jpg....

I think 25 is wrong....just count all the squares above or below the diagonal squares. The ans is 15.

For the second question, i think there is no other way other than trying all the combinations. It would help to uniquely identify every junction uniquely (numbers or alphabets) so as to avoid a retrace!
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you said the magic word... combinations... :o)

is there a way to solve this using nCk or permutations? you will always have to walk up 3 streets and over 2....

i just don't think the GMAT wants us to trace a grid, they are testing us on something here
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Powerprep PS Grids 25 Jun 2007, 00:07
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first one - 6C2 = 15 :)
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AugiTh
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Powerprep PS Grids 25 Jun 2007, 00:24
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Ah nice one grad_mba....this problem (the first one) is analogous to the handshake problem!
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AugiTh
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Powerprep PS Grids 25 Jun 2007, 00:33
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for the second one I guess combinations could be a way out
Hmmmm....food for thought!



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