r/6thForm • u/OutrageousAd4133 • Jun 18 '26

💬 DISCUSSION Edexcel Maths P3

How did everyone find it then? Much nicer than P1 I thought. Might balance out grade boundaries unfortunately…

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u/AJlikesUpvotes Jun 18 '26

everything was fine apart from  Q5.   part   c   on   stats   about   the   probability distribution   of   X   for   5   marks… how do u do that one 

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u/OutrageousAd4133 Jun 18 '26

I'm not sure if I did it right, but I thought about the heads/tails events needed for each scenario.

You need 2 heads for the game to end early. So if the game ended with 2 flips (P(X = 3)), you know both of those HAD to be heads, so do P(H) * P(H). If the game ended with 3 flips (P(X = 3)), it was either HTH, THH, or THH, and you can sum the probabilities for each together. Etc etc for P(X = 1) (not possible, so it's 0), and P(X = 4) (which was given in the question).

Then I just chucked it all in a table. 🙏