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Thursday, April 30, 2009

Random Thoughts: A Few Brain Teasers

Sharing some brain teasers I found interesting. See how many you can figure out yourself:

Problem 1: The Missing Dollar
Three guests check into a hotel room. The normal charge for one night is $30, so each guest pays $10. Later the owner said that there's a promotion and the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn't know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 for himself.
Now that each of the guests has been given $1 back, each has paid $9, bringing the total paid to $27. The bellhop has $2. If the guests originally handed over $30, what happened to the remaining $1?

Problem 2: Cut the Loss
One day a customer came to Tom's store. He collected $20 worth of merchandize, and then gave Tom a $50 bill. Since Tom didn't have enough change, he went to Charlie's store next door and exchanged the $50 bill into changes. Then he gave the customer $30 change. Shortly after the customer left, Charlie came to Tom and told him that the $50 bill was counterfeit money. So Tom immediately gave Charlie another $50 bill in exchange. So after all, how much money did Tom lose from this incident? Was it $50, $80, or $100?

Problem 3: Green Onion Vendor
A customer came to the green onion vendor and asked about the price of the green onions. The vendor said that the green onions sell for one dollar per pound. Since he had a total of 100 pounds, it would cost one hundred dollars to buy them all. The customer then asked if the vendor would consider selling green onion stems and leaves separately. The vendor told him that the green onion stems would sell for 70 cents and the green onion leaves would sell for 30 cents. The customer then decided to buy 50 pounds of green onion stems and 50 pounds of green onion leaves. The vendor then calculated as the following:

50 x 0.7 = 35, 50 x 0.3 = 15, 35 + 15 = 50

So the customer paid $50 and left. Now the green onion vendor was very confused: how come the customer was able to take away his $100 worth of green onions for only $50?

Problem 4: Find the Odd Ping Pong Ball
You have 12 ping pong balls. One of them is slightly heavier OR lighter than the others. You also have a balance scale. How can you find the odd ball out, and if it is heavier or lighter, in only 3 weighings. Please help!

Problem 5: Silver Utensils Problem
Bill wanted to buy some silver utensils, so he went to the utensil store and then found out that he only had enough money to buy 21 forks and 21 spoons, or 28 knives only. Since he needs to buy the same number of forks, spoons and knives to make complete sets, and he would really prefer to use up all the money he had brought, can you help him out?

Video of the Day:

A great review of year 2011 based on what people searched in Google: