Question

In a Piggy bank there are 100 coins of 50 paise, 50 coins of Rs 1, 20 coins of Rs 2 and 10 coins of 5. If after shaking the bank properly and turning it downward the probability of falling a coin is at random. Find the probability that coin fallen is:

(i) 50 paise

(ii) Not Rs 5.

Answer 1

Number of 50 paise coins = 100

Number of Rs 1 coins 50

Number of Rs 2 coins 20

Number of Rs 5 coins = 10

Total number of coins 

= 100 + 50 + 20 + 10 = 180

∴ Total number of all possible outcomes = 180

(i) The bank contains 100 coins of 50 paise.

∴ The number of favourable outcomes = 100

∴ The probability of the coin fallen is a coin of 50 paise

∴ P(50 paise coin) = \(\frac { 5 }{ 9 }\)

(ii) The number of Rs 5 coins = 10

∴ Probability of Rs 5

= \(\frac { 10 }{ 180 }\) = p(Rs 5 coin) = \(\frac { 1 }{ 18 }\)

The probability that the coin fallen is not Rs 5.

P(not a coin of Rs 5) = 1 – P(Rs 5 coin)

= 1 – \(\frac { 1 }{ 18 }\) = \(\frac { 17 }{ 18 }\)