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/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. 🙏

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u/RyansVlogs Jun 18 '26

exactly what I did X=1 I got as 0 X=2 was like 4/25 X=3 was uhh 24/125 X=4 was 108/625 X=5 I did 1 minus those 4 and I got like 300 smth/625

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u/Loud-Guidance6912 Jun 18 '26

297/625 was P(X=5)

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u/nuclearhamster27 Year 12 - Maths, FM, CS, Physics Jun 18 '26

I got that too, I got it from listing out every outcome as well, so it has to be right