Today’s Brain Challenge
Challenge your brain today with riddles, puzzles and problems.
The Rotating Cube Problem
Problem: Each face of a cube is marked with a letter. The cube is shown in 3 different positions. Determine the letter on the face opposite: • the face marked X. • the face marked A. • the face marked C. Solution Comparing the cube in positions 1 and 3, we see that …
Does the Barber shave himself?
In a town in which every man is clean-shaven each male either shaves himself or is shaved by the barber. The barber is a man who shaves everyone who does not shave himself (and only those who do not shave themselves). Does the barber shave himself? To ensure that you see the paradox, think about …
Benjamin Bannecker’s Problem
The following problem was found in Benjamin Banneker’s only remaining journal: Divide 60 into four such parts that the first being increased by 4, the second decreased by 4, the third multiplied by 4, the fourth part divided by 4, that the sum, the difference, the product and the quotient shall be one and the same number. Can you find the …
What Countries Have the Oldest Population?
The median age divides a population into two parts of equal size, so that half the people are below the median age and half are above it. The table shows the median age of the population in 7 different countries, in 2020 (listed alphabetically): Brazil, China, India, Japan, Nigeria, United Kingdom and United States. Which …
Was Manhattan a good purchase?
A common myth asserts that the Dutch settlers purchased Manhattan Island for $24 in 1626 from the aboriginal people. If that $24 were invested in 1626 at the current interest rate of 7% per annum, what would be the approximate value of that investment today? A) $13 trillion B). $1.3 trillion C). $13 billion D) …
Teeha and the Tealeaves
To prepare for his fortune-telling tea party, Teeha brewed a giant pot of tea by tossing teabags into a large cauldron of water. The 100-lb mixture was 99% water by weight. Teeha then boiled the mixture until it was only 98% water by weight. What was the weight of the mixture when it was 98% …
What’s the probability?
Two 10-sided dice have faces numbered from 1 through 10. What is the probability that a toss of the dice will yield a multiple of 2 on one die and a multiple of 3 on the other? Answer: Half the numbers on each die are multiples of 2, so the probability that a particular die …
How rare is an IQ of 140?
An IQ of 140 is achieved by: A) 1 in every 261 people. B) 1 in every 1024 people. C) 1 in every 5206 people. Answer: A person who registers an IQ of 140 on an IQ series of tests for which the mean is 100 and standard deviation 15, is in the 99.616957th percentile. …
How many golf balls would it take to fill spaceship earth?
A golf ball is approximately spherical with a radius of about 2 cm. Spaceship Earth is approximately a sphere of radius of 27 m. About how many golf balls would it take to fill Spaceship Earth? A) 20,000,000 B). 200,000,000 C). 2,000,000,0000 Answer: The volume V of a sphere is given by V = (4/3)πR3 …
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