Missing Numbers

Math on October 12th, 2009 Comments Off

Problem Solve this simple arithmetic by replacing each # sign with a different digit, 1-9, using each digit only once. ## represents a two-digit number. ## x # —– ## + ## = ## Solution When filled in correctly, the equation is: 17 x 4 —– 68 + 25 = 93 If you have a [...]

Penny Problem

Math on September 28th, 2009 Comments Off

Problem You are given ten pennies arranged like this picture. Move three of them so that the arrow in the opposite direction. Solution Take the top penny and move it to a new row, in the center, under the bottom row into the following configuration: x       x x        x       [...]

Related Rates

Math on September 21st, 2009 Comments Off

Problem While this problem looks straight from a differential calculus textbook, it requires no advanced math. Two bugs sit on either side of a bubble. The radius r of the bubble is expanding with dr/dt=3 cm/s. The distance between the bugs is d and they sit on either side of a 60 degree arc, find [...]

Balance Problem

Math on September 15th, 2009 Comments Off

Problem You are given 10 balls, which are all identical. One ball is either heavier or lighter than the rest. Using a balance three times, can you determine which ball is different, and whether the weight is heavier or lighter? This requires no advanced math or tricky way of using the balance. Think it’s too [...]