A man has 3 unique coins such that the probability of obtaining a head when the coin is flipped is 1 10 , 2 10 and 3 10 , respectively. If he flips each of the 3 coins once, the probability that at least 1 heads appears is p . What is the value of 1000 p ?

Question

hartnn · Answer

do you have some idea on how to start ? 
how to solve 'atleast 1' type of Questions ?

anonymous · Answer

if i have any idea, then y i should post the question yaar.
really no idea

hartnn · Answer

okk...so the rule is,
P (atleat 1) = 1 - P (none)
now you need to find, P(none) = probability that in 3 flips no head appears.
ok till here ?

anonymous · Answer

yup

hartnn · Answer

probability that in 3 flips no head appears
 = probaility that head doesn't appear (means tail appears) on 1st flip AND  probaility that head doesn't appear (means tail appears) on 2nd flip AND  probaility that head doesn't appear (means tail appears) on3rd flip
right ?

anonymous · Answer

yup

hartnn · Answer

so, if you flip 1st coin, what is the probability of getting tail(not getting head) ?

anonymous · Answer

no idea

hartnn · Answer

is this your 1st probability Question ?

anonymous · Answer

1/2

hartnn · Answer

that woud be true if the coin was unbaised, but here the coin is biased , and we r given P (Head) , so, P (Tail) = 1- P(Head) =... ?

anonymous · Answer

1-p

hartnn · Answer

no..for 1st coin P (Head) = 1/10 given
so, P (Tail) = 1-1/10 = 9/10
got this ?

anonymous · Answer

k..got it

hartnn · Answer

for 2nd and 3rd coin, what will be P (Tail) =??

anonymous · Answer

1-2/10
1-3/10

anonymous · Answer

8/10
&7/10

hartnn · Answer

correct, 
probability that in 3 flips no head appears
 = probaility that head doesn't appear (means tail appears) on 1st flip AND  probaility that head doesn't appear (means tail appears) on 2nd flip AND  probaility that head doesn't appear (means tail appears) on3rd flip
 =P (Tail) for 1st coin*P (Tail) for 2ndcoin*P (Tail) for 3rd coin
= ..... ?

anonymous · Answer

(9/10)*(8/10)*(7/10)

hartnn · Answer

yes, that is p 
p = (9/10)*(8/10)*(7/10)
so, 1000p = 1000 * (9/10)*(8/10)*(7/10) =...?

anonymous · Answer

9*8*7

hartnn · Answer

$\checkmark $
i hope you understand all steps..

anonymous · Answer

yup
thank u @hartnn

hartnn · Answer

welcome ^_^