Topscore 3 qr 40

[notsowisetooth]

With one fair die, find the probability of throwing two fours in five attempts?

I did: (1/6)^2 * (5/6)^3.

but topscore says the answer is (10*125)(36*216), which is like my answer except that it has an extra 10 there....where the heck did that come from?

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[fsddsms]

With one fair die, find the probability of throwing two fours in five attempts?

I did: (1/6)^2 * (5/6)^3.

but topscore says the answer is (10*125)(36*216), which is like my answer except that it has an extra 10 there....where the heck did that come from?

probability of throwing two fours in five attempts = 5!/ 2!(5-2)!) (1/6^2)(5/6)^3

5! / 2!(5-2!) = 5 x 4 / 2 x 1 = 5 x 2 = 10 <~~~ there's the missing 10. remember it's nCr multiplied to those probabilities because you can get the two fours in various combinations during the five attempts.

Hope that helps!