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Mathematics

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24 likes 7.0
(Challenging)
The Famous Hole in a Sphere in Mathematics
This incredible problem was first made famous by Martin Gardner with his 'Mathematical ...
Added about 1 year ago by Valentin currently with 48 comments
22 likes 4.9
(Moderate)
The fake coin in Mathematics
You have 9 coins which all look identical but 1 of them weight less than the others. Yo...
Added about 1 year ago by jakab922 currently with 21 comments
17 likes 4.2
(Moderate)
100 Balls, 2 Jars in Mathematics
You have 2 jars, 50 red balls, and 50 blue balls. You need to put all the balls into t...
Added about 1 year ago by kash currently with 16 comments
16 likes 5.9
(Moderate)
Mutilated Chessboard Problem in Mathematics
Suppose a standard 8x8 chessboard has two diagonally opposite corners removed, leaving ...
Added about 1 year ago by copter currently with 22 comments
15 likes 6.0
(Challenging)
Greatest Area in Mathematics
A farmer challenges an engineer, a physicist, and a mathematician to fence off the larg...
Added about 1 year ago by johnp currently with 31 comments
15 likes 6.2
(Challenging)
Simple 24 in Mathematics
Why is that if p is a prime number bigger than 3, then p^2-1 is always divisible by 24 ...
Added about 1 year ago by dani3l currently with 35 comments
13 likes 3.2
(Fairly Easy)
The Easy Sum of 1..100? in Mathematics
Quick,without using a calculator, what is the sum of all numbers between 1 and 100 incl...
Added about 1 year ago by Valentin currently with 32 comments
13 likes 4.5
(Moderate)
Left Hands Only in Mathematics
Assume there are approximately 6,000,000,000 (6 billion) people on Earth. What would yo...
Added about 1 year ago by vette982 currently with 47 comments
13 likes 5.4
(Moderate)
Cutting Numbers in Mathematics
When is Seven half of Twelve?
Added about 1 year ago by Tsion currently with 42 comments
13 likes 3.0
(Fairly Easy)
What number is next? in Mathematics
What number comes next in this sequence? 4, 20, 56, 120, 220, ?
Added 10 months ago by ace currently with 46 comments
12 likes 6.2
(Challenging)
Lockers in Mathematics
A high school has a strange principal. On the first day, he has his students perform an...
Added about 1 year ago by copter currently with 35 comments
12 likes 5.5
(Moderate)
Divide 1 to 20 in Mathematics
What is the smallest whole number that can be divided by any number from 1 to 20 (inclu...
Added 11 months ago by Dusty currently with 23 comments
10 likes 4.4
(Moderate)
Running Race in Mathematics
Phil and Sal race each other for 100 yards. Sal wins by 10 yards. They decide to race ...
Added about 1 year ago by copter currently with 26 comments
10 likes 6.0
(Challenging)
Farmer's Market in Mathematics
You're a farmer. You're going to a market to buy some animals. On the market there are ...
Added about 1 year ago by jaX currently with 37 comments
10 likes 6.3
(Challenging)
Birthday Problem (Classic) in Mathematics
A classic problem. How many people do you need to have in a room so that the probabi...
Added 11 months ago by Dusty currently with 16 comments