prachich1987 wrote: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.

Note that there is no restriction about which color can precede any green tile. Thus green may appear anywhere in the series. Now looking at the statements we can say that the answer will be E, because there is no definite regularity in the series or we can go for a detailed analysis.

Statement 1: The 18th tile in the row is not yellow.
Thus it may be either red or green. Hence the color of 24th tile may depend on the color of this 18th tile.

Not sufficient

Statement 1: The 19th tile in the row is not Green.
Thus it may be either red or Yellow. Hence the color of 24th tile may depend on the color of this 19th tile.

Not sufficient

1 & 2 Together: From statement 1, 18th is either red or green which means 19th is either Green or Yellow. But from statement 2, 19th tile is either Red or Yellow or Green. Combining this two, we get that 19th tile is either Yellow or Green.

Not sufficient

The correct answer is E.

prachich1987 wrote:consider that the following non-pattern is also possible:

Green, Yellow, Red, Green, Green, Green, Green . . .

Thank you.
Missed that point, edited the reply.