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 Smokey's Smokes (Posted on 2010-06-03)
A store sells three brands of cigarettes: \$3.15 Star lights, \$4.30 Vegas slims, and \$5.20 Royal 100's. (Tax included) A man named Smokey walks into the store, and buys 2 packs of cigarettes, one pack for himself and the other pack for a friend. He hands the cashier a \$20 note, and is returned a few bills and 3 coins in change (exclude dollars or half dollars). What's the probability, that the man smokes Royal 100's?

 No Solution Yet Submitted by John zadeh No Rating

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 solution | Comment 2 of 6 |
In order for exact change to include only three coins of US currency, Smokey must have purchased either:
1. One pack of Star lights and one pack of Vegas slims
purchase: \$ 7.45
change: \$12.55
coins: 55 cents = two quarters and one nickle
2. Two packs of Vegas slims
purchase: \$ 8.60
change : \$11.40
coins: 40 cents = one quarter, one dime and one nickle

3. Two packs of Royal 100's
purchase: \$10.40
change: \$ 9.60
coins: 60 cents = two quarters and one dime
There is then a 1/3 probability Smokey smokes Royal 100's.

Without half dollar or dollar coins, the change from the other possible purchases can not be given as three coins of US currency:
• two packs of Star lights
purchase: \$ 6.30
change: \$13.70 (70 cents)
• one pack each, Star lights and Royal 100's
purchase: \$ 8.35
change: \$11.65 (65 cents)
• one pack each, Vegas slim and Royal 100's
purchase: \$ 9.50
change: \$10.50 (50 cents)

Edited on June 3, 2010, 12:43 pm
 Posted by Dej Mar on 2010-06-03 12:39:26

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