There are 100 sealed envelops in a box, 10 of them contain a cash prize of 100 each, 100 of them contain a cash prize of 50 each and 200 of them contain a cash prize of 10 each and rst do not contin any cash prize. If they are well shuffled and an evelope is picket up out, What is the probabiilty that it contains no cash prize?

Explanation

Total number of sealed envelopes in a box, n(S)=1000
Number of evelopes containing cash prize=10+100+200=310
Number of envelops containing no cash prize,
`n(E )=1000-310=690`
`P(E )=(n(E ))/(n(S))=(690)/(1000)=(69)/(100)=0.69`