You are a cook in a remote area with no clocks or other way of keeping time other than a four-minute and a seven-minute hourglass. On the stove is a pot of boiling water. Jill asks you to cook a nine-minute egg in exactly 9 minutes, and you know she is a perfectionist and can tell if you under cook or overcook the egg by even a few seconds. How can you cook the egg for exactly 9 minutes?
1. Flip both hourglasses over and drop the egg into the water. 2. When the 4-minute timer runs out, flip it over (4 minutes elapsed, 3 remaining on the 7-minute timer). 3. When the 7-minute timer runs out, flip it over. (7 minutes elapsed, 1 remaining in the 4-minute timer) 4. When the 4-minute timer runs out, flip the 7-minute timer over. (8 minutes elapsed. 6 minutes remained in the 7-minute timer, but flipping it over leaves one minute’s worth of sand on top. When it runs out exactly nine minutes will have elapsed.)
7. The digits represent the number of letters in each word of the puzzle. “What” has four letters, “digit” has five letters, “should” has six letters, etc. The last word is “numbers” which has seven letters.
You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, how can you determine which coin is counterfeit using the scale only twice?
First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it’s the counterfeit. If they’re equal weight, the third coin is the counterfeit.
I can help you have some fun, Sometimes I get stronger from the sun, If you never give me a break, You will find I never wake, I am optimistic on one side, I can be short, fat, tall or wide, Rectangle and cylinder are two of my shapes, And I can even help you make video tapes, Sometimes you must wait for me to get ready, Just hold on for a few hours and be steady, I can help you get around the mall, Or help you make a telephone call.
A battery. Games and other entertainment devices run on batteries. Batteries can be charged using solar power, which is from the sun. If you use a battery-powered device long enough, the battery will die. Batteries have a plus side and can be all shapes and sizes. They can power scooters and Segways commonly used in malls and your cell phone requires a battery to function.