(Q9)A Kiddy bank contains hundred 50p coins, fifty Rs. 1 coins, twenty Rs. 2 coins and ten Rs. 5 coins. If it is equally likely that one of the coins will fall out when the bank is turned upside down, what is the probability that the coin (i) will be a 50 p coin? (ii) will not be a Rs. 5 coin ?

Answer :

(i) Number of 50 p coins = 100

Number of Rs. 1 coins = 50

Number of Rs. 2 coins = 20

Number of Rs. 5 coins = 10

Total number of coins =

Number of total outcomes for a coin to fall down = .

Number of outcomes favourable to 50 p coins to fall down = .

∴ Probability of a 50 p coin to fall down =
No. of favourable outcomes
No. of total outcomes
 =
=
5

(ii) Let P(E) be the probability for a Rs. 5 coin to fall down.

Number of outcomes favourable to Rs. 5 coin = .

∴ Probability of a Rs. 5 coin to fall down =
No. of favourable outcomes
No. of total outcomes
 =
=
1

Then P(Ē) is the probability of a coin which fall down is not a Rs. 5 coin.

Again P(E) + P(Ē) = 1

∴ P(Ē)= 1 - P(E) = 1 -
1
 =