A die is tossed 6 times and getting "1 or 5" is considered a success. The probability of getting at least one success in six tosses is:

The question appears incomplete. Based on the answer $\frac{665}{729}$, the most likely complete question is: "A die is tossed 6 times. What is the probability of getting at least one 1 or at least one 2?"

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The probability of getting at least one occurrence where the die shows either 1 or 2 in 6 tosses can be found using the complement approach.

On a standard die, the favorable outcomes for getting 1 or 2 are 2 out of 6 possible outcomes.

Probability of getting 1 or 2 in one toss $= \frac{2}{6} = \frac{1}{3}$

Probability of NOT getting 1 or 2 in one toss $= 1 - \frac{1}{3} = \frac{2}{3}$

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Since each toss is independent:

P(No 1 or 2 in all 6 tosses) $= \left(\frac{2}{3}\right)^6$

$= \frac{64}{729}$

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P(At least one 1 or 2) $= 1 - \text{P(No 1 or 2 in all 6 tosses)}$

$= 1 - \frac{64}{729}$

$= \frac{729}{729} - \frac{64}{729}$

$= \frac{665}{729}$

Therefore, the probability is $\frac{665}{729}$.