Question

A purse contains two sovereigns, two shillings and a metal dummy of the same form and size; a person is allowed to draw out one at a time till he draws the dummy: find the value of his expectation.

Answer 1

Given: purse contains two sovereigns, two shillings and a metal dummy

To find: the value of his expectation

Sol: Here $X$=number of dummy drawn

The probability distribution for the above event is as follows:

$X$	$0$	$1$
$P\left(X\right)$	$\frac{4}{5}$	$\frac{1}{5}$

Expected value = $0\times \frac{4}{5}+1\times \frac{1}{5}=\frac{1}{5}=0.2$