Question

A piggy bank consists hundred 50p, 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
(1)will be a 50p coin?
(2) will not be a Rs. 5 coin?

Answer 1

Total number of coins in a piggy bank = 100 + 50 + 20 + 10 = 180
Therefore, Total number of elementary events = 180
(i) There are one hundred 50 paise coins in the piggy bank.
Therefore, Favourable number of elementary events =100
Hence, P(falling out of a 50p coin) $=\frac{100}{180}=\frac{5}{9}$
(ii) There are 100 + 50 + 20, i.e., 170 coins other than Rs 5 coin. Therefore, Favourable nunber of elementary events =170
Hence, P(falling out of a coin other than Rs. 5 coin) $=\frac{170}{180}=\frac{17}{18}$