## probability of coin toss, please help :)

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Fa23
Garter
Posts: 12
Joined: Wed Nov 10, 2010 5:17 pm

### probability of coin toss, please help :)

if 2 coins are tossed 20 times, how many of those tosses would you expect to result in both coins landing heads up? show your calculations.

my attempt:

for each toss the probability of heads is 0.5
therefore the probability of heads for both coins is 0.5 * 0.5 = 0.25

5/20 times the coins will both be heads up.

is this all correct? any help would be appreciated. thanks

JackBean
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm
seems fine to me

why are there so many math questions now?
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

Rap
Death Adder
Posts: 60
Joined: Tue Jan 18, 2011 5:57 pm
5 is the average number of times two heads will turn up. It is possible for anything from zero to 20 to happen though.

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