In a single row of yellow, green and red colored tiles, every red tile is preceded immediately by a yellow tile and every yellow tile is preceded immediately by a green tile. What color is the 24th tile in the row?
(1) The 18th tile in the row is not yellow.
(2) The 19th tile in the row is not green.
I'm interested to see your thoughts...
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Colored Tiles
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fourteenstix
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Hi fourteenstix,
What is the source of this question? I ask because the "intent" of this question might not match the "logic" of this question. The information at the beginning of the prompt is "causal" but only deals with tiles that PRECEDE other tiles; we have to deduce what tiles can FOLLOW other tiles. We know what comes immediately before a red (a yellow) and we know what comes immediately before a yellow (a green), but we're not told what comes before a green.
Up-Front Deductions:
A Green can be followed by another Green or a Yellow (but not a Red)
A Yellow can be followed by a Green or a Red (but not a Yellow)
A Red can be followed by a Green (but not a Yellow or Red)
We're asked for the 24th Tile....
Fact 1: 18th = NOT Yellow, so 18th = Green OR Red
If 18th = Red
we would have G, G, G, G, G to infinity, so the 24th Tile = GREEN
If 18th = Green
we COULD have G, G, G, G, G, Y, so the 24th Tile = YELLOW
Inconsistent = INSUFFICIENT
Fact 2: 19th is NOT Green, so 19th = Yellow OR Red
If 19th = Red
we would have G, G, G, G, G, so the 24th Tile = GREEN
If 19th = Yellow
we could have R, G, G, G, Y so the 24th Tile = YELLOW
Inconsistent = INSUFFICIENT
Combining Facts:
18th = Green OR Red
19th = Yellow OR Red
Since Red can only be followed by GREEN, the 18th Term CAN'T be Red!
So, 18th = Green and
19th = Yellow
we could have G, G, G, G, G, so the 24th = GREEN
we could have G, G, G, G, Y, so the 24th = YELLOW
Inconsistent = INSUFFICIENT
Final AnswerE
GMAT assassins aren't born, they're made,
Rich
What is the source of this question? I ask because the "intent" of this question might not match the "logic" of this question. The information at the beginning of the prompt is "causal" but only deals with tiles that PRECEDE other tiles; we have to deduce what tiles can FOLLOW other tiles. We know what comes immediately before a red (a yellow) and we know what comes immediately before a yellow (a green), but we're not told what comes before a green.
Up-Front Deductions:
A Green can be followed by another Green or a Yellow (but not a Red)
A Yellow can be followed by a Green or a Red (but not a Yellow)
A Red can be followed by a Green (but not a Yellow or Red)
We're asked for the 24th Tile....
Fact 1: 18th = NOT Yellow, so 18th = Green OR Red
If 18th = Red
we would have G, G, G, G, G to infinity, so the 24th Tile = GREEN
If 18th = Green
we COULD have G, G, G, G, G, Y, so the 24th Tile = YELLOW
Inconsistent = INSUFFICIENT
Fact 2: 19th is NOT Green, so 19th = Yellow OR Red
If 19th = Red
we would have G, G, G, G, G, so the 24th Tile = GREEN
If 19th = Yellow
we could have R, G, G, G, Y so the 24th Tile = YELLOW
Inconsistent = INSUFFICIENT
Combining Facts:
18th = Green OR Red
19th = Yellow OR Red
Since Red can only be followed by GREEN, the 18th Term CAN'T be Red!
So, 18th = Green and
19th = Yellow
we could have G, G, G, G, G, so the 24th = GREEN
we could have G, G, G, G, Y, so the 24th = YELLOW
Inconsistent = INSUFFICIENT
Final AnswerE
GMAT assassins aren't born, they're made,
Rich
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fourteenstix
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It was an MGMAT question from a CAT that I took yesterday. You keenly noticed that the stem is not giving us a patter; something I failed to see and thus answered C.
I just thought this question was too less-than-straightforward for the GMAC to do something similar. I was a bit frustrated by the trickery of it.
I just thought this question was too less-than-straightforward for the GMAC to do something similar. I was a bit frustrated by the trickery of it.
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Hi fourteenstix,
I absolutely agree; the GMAT is not likely to give you a question that is designed in this way. While you will see some sequence-based questions, those questions tend to be well-defined so that you don't have to spend too much time figuring out how the sequence "works." Like typical sequence questions though, this prompt did require you to figure out the pattern behind the sequence.
GMAT assassins aren't born, they're made,
Rich
I absolutely agree; the GMAT is not likely to give you a question that is designed in this way. While you will see some sequence-based questions, those questions tend to be well-defined so that you don't have to spend too much time figuring out how the sequence "works." Like typical sequence questions though, this prompt did require you to figure out the pattern behind the sequence.
GMAT assassins aren't born, they're made,
Rich
