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New Challenging Brainteasers
1. Refrigerator in a Room
You are locked
into an empty room with only a working refrigerator plugged into a standard
electric outlet. The room is uncomfortably warm, and your goal is to
cool the room to the maximum extent possible. What can you do? (Click
for Solution)
2. Weight on Moon and Earth
Why should such a simple question create such complexities? Experience shows that if a candidate doesn’t immediately get the solution to this puzzle, it is very unlikely he or she will ever get it without a hint. The trap here is that the mind immediately goes to the main difference between the earth and the moon—the difference in gravitational pull—and then stops there.
What weighs more
on the moon than on the earth? (Click
for Solution)
3. Two Surgical Gloves, Three Patients
A one-armed surgeon needs to operate on three patients, one after another. But the surgeon has only two individual surgical gloves. How can the surgeon operate on the three patients in turn without risking infection for the patients or for himself? (Click for Solution)
4. Balancing Gold
A gold bar balances
with nine-tenths of 1 pound and nine-tenths of a similar gold bar. How
much does each gold bar weigh?
(Click
for Solution)
5. Semiconductor Wafers
In a custom microchip
processing plant, workers shape 1 gram packages of Silicon semiconductor
material into custom microprocessor wafers. During the manufacturing
process, not all the Silicon is used. For every five wafers the plant
fabricates, there is enough extra Silicon to make one additional wafer.
Suppose a worker is presented with 25 grams of Silicon. What is the
maximum number of wafers she can make? (Click
for Solution)
6. Lemonade Stand Susie, the best student in arithmetic in her grade school, started a gourmet lemonade stand with a unique payment policy. Instead of taking payment for the lemonade, Susie had this policy: a customer would open the cash drawer, match whatever amount of money was in there, and then take out 20 cents. The first customer of the day does just that: matches whatever is in the cash drawer and then takes out 20 cents. The second customer of the day does the same, as does the third. The fourth customer, however, looks at the cash drawer and calls out, “Hey, the cash drawer is empty. There’s not a cent in here.” The question
is how much money did Susie have in the cash drawer to start? (Click
for Solution)
7. Walking and Cycling John and Fred have a dilemma. They need to get back to town as quickly as possible, but they only have one bicycle between them. And, of course, you can travel faster on the bike than you can by walking. John says, "We'll leave at the same time. You start walking, and I'll ride the bike for a mile. Then I'll leave it by the side of the road, while you keep walking. When you get to the bike, you get on it, and you ride for a mile, and then you leave it by the side of the road. When I get to it, I'll ride another mile. We'll keep leapfrogging like this until we get to town. "Since we'll be riding part of the way and walking part of the way, each of us will have a higher average speed than if we walked, so we'll get there faster,” John explains. Fred says, "That isn't going to do any good, you dope! Think about it. Between the two of us, one or the other is going to walk every inch of the way from here to town. So, we can't possibly get there any faster than if we just walked all the way and didn't use the bike at all." Who is right? John, who think they will get there faster or Fred, who thinks it doesn’t make a difference? Or are they both wrong? (Click for Solution) 8. Fishy Business
A boy goes and buys a one-piece fishing pole that is 6' 3" long. As he goes to get on the bus, the bus driver tells him that he can't take anything on the bus longer than 6'. The boy goes back to town, buys one more thing, and the bus driver allows him on the bus. The boy did not damage the fishing pole in any way.
What did he buy, and what did he do with it? (Click for Solution)
You are a park
ranger who manages a tourist site with breathtaking views from the top
of a mountain. Your visitors typically park at the visitor’s center
and then walk up a fairly steep unpaved path to the spot with the best
view. You have been ordered by the head ranger to provide some accommodation
for visitors using wheelchairs to get to the best viewpoint. You are
technically exempt from federal accessibility laws. Tell me your best
ideas for accommodating the disabled visitors? Click
for Solution)
10. Getting Better Every Day
If you improve your capabilities by 1 percent per day, in how many days will you be twice as capable as you are today? (Click for Solution)
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