A man draws 2 balls from a bag containing 3 white and 5 black balls. If he receives Rs.70 for every white ball he draws and Rs.7 for every black ball. Find his expectation.

1. A man draws 2 balls from a bag containing 3 white and 5 black
balls. If he receives Rs.70 for every white ball he draws and
Rs.7 for every black ball. Find his expectation.
Solution
Possibilities P(X) X X.P(X)
2 white balls
𝟑𝒄𝟐
𝟖𝒄𝟐
=
𝟑
𝟐𝟖 140 15
1 white and
1 black ball
𝟑𝒄𝟏
× 𝟓𝒄𝟏
𝟖𝒄𝟐
=
𝟏𝟓
𝟐𝟖
77 41.25
2 black balls 𝟓𝒄𝟐
𝟖𝒄𝟐
=
𝟏𝟎
𝟐𝟖
14 5
E(X) = 61.25
His expectation is Rs.= 61.25