Give me any 2 digit number that ends in 5, and I’ll square it in my head! 452 = 2025 852 = 7225, etc....
Continue reading...algebra
Red-Black Card Trick
Here’s a pretty easy card trick that you can do that can also be pretty surprising. Here’s how the trick...
Continue reading...One Equals Zero: Integral Form
Consider the following integral: INTEGRAL (1/x) dx Perform integration by parts: let u = 1/x , dv = dx du = -1/x2 dx...
Continue reading...Difference of Squares
You have all learned that a2 – b2 = (a + b)(a – b) But perhaps you haven’t thought about how to...
Continue reading...Magic 1089
Here’s a cool mathematical magic trick. Write down a three-digit number whose digits are decreasing. Then reverse the digits to...
Continue reading...Multiplication by 11
Multiplication by 11 is easy! To multiply by a 2-digit number add the two digits and place the sum in...
Continue reading...Magic Squares, indeed!
Perhaps you’ve seen the magic square 8 1 6 3 5 7 4 9 2 which has the property that all rows,...
Continue reading...Leapfrog Addition
Here’s a nice mathematical magic trick based on properties of the Fibonacci sequence. Give your friend a card with ten blank lines, numbered 1...
Continue reading...Proofs without Words
There are many facts which can be proved just by looking at a picture! For instance:x2 – y2 = (x+y) (x-y)is illustrated...
Continue reading...Pascal’s Triangle
Consider the triangle in Figure 1, called Pascal’s triangle. It consists of numbers where each entry is the sum of the...
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