A piggy bank contains hundred 50p coins, fifty ₹ 1 coins, twenty ₹ 2 coins and ten ₹ 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 ₹ 5 coin?
Solution:
Total number of coins in the piggy bank:
100 (50p coins) + 50 (₹1 coins) + 20 (₹2 coins) + 10 (₹5 coins) = 180 coins
(i) Probability of drawing a 50p coin:
There are 100 coins of 50p.
P(50p coin)=100/180 = 5/9
(ii) Probability of not drawing a ₹5 coin:
There are 10 coins of ₹5. So, the coins that are not ₹5 = 180 – 10 = 170 coins.
P(Not ₹5 coin) = 170/180 = 17/18