# Two wallets containing coins. The first wallets containing five pieces of five hundred rupiahs and two pieces of hundreds rupiahs. other wallets containing one piece of five hundred rupiahs and three pieces of hundreds rupiahs. if the coins are taken randomly from one wallets, determine opportunities to earn coins hundreds rupiahs

1
by Ayi

2015-04-27T13:43:55+05:30

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Probability of getting a 100 Rs coin from the 1st wallet
= number of coins of Rs 100 / total number of coins     = 2/7

probability of getting a 100 Rs coin from the 2nd wallet
= number of coins of Rs 100 /total number of coins = 3 / 8

Probability of selecting 1st wallet =  1 / number of wallets = 1/2
probability of selecting 2nd wallet = 1/2

we apply the conditional probability theorem here.

P (A AND B) = P(A) *  P (B | A)

here event A = selection of a wallet 1 or 2.
event B = selection of hundred Rupiah coin

Probability(getting a Hundred Rupiah coin)
= P(selection of first wallet) * P (getting a Hundred Rs coin from first wallet)
+ P(selection of 2nd wallet) * P(getting a Hundred Rs coin from 2nd wallet)
= 1/2 * 2/7  + 1/2 * 3/8
= 37/112

the opportunities are 37 in 112  or about 33%

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