Mathematics - Online Test

Let X denote same number of heads Both will get.

So X can take values 

X=0 ( both get 0 number of head)

X =1 ( both get 1 head)

X = 2 ( both get 2 heads)

X = 3 ( both get 3 heads)

X = 4 ( both get 4 heads)

So , P(X = 0 ) =Probabilty of getting no heads= 1/16 × 1/16 = 1/256      [by multiplication theorem  P(Xi∩$\cap$ Xj) = P(Xi).P(Xj) ]

P(X=1) =  Probabilty of getting 1 head = 4/16 × 4/16 = 16/256

P(X =2) = Probabilty of getting 2 heads =  6/16 × 6/16 = 36/256

P ( X = 3) =Probabilty of getting 3 heads=4/16 × 4/16 = 16/256

P( X= 4) =Probabilty of getting 4 heads = 1/16 × 1/16 = 1/256

Therefore P ( both get same number of head in a throw of 4 coins each )

= P(X=0) + P(X=1) + P(X=2) + P(X =3) + P(X =4)

= 1/256 + 16/256 + 36/256 + 16/256 + 1/256

= 70/256 = 35/128

When three dice  are rolled, total number of outcomes =n(S)=n=63 =216

It is given that the numbers on all the three dice are identical

Hence the favourable outcomes are (1,1,1),(2,2,2),(3,3,3),(4,4,4),(5,5,5),(6,6,6)

Hence no. of  favourable outcomes=m=6

Hence required probability=mn=6216=136