Interesting Math Trivia
Here's an interesting math trivia trick to impress a friend, a group, or class. Tell the person (or class) to think of their birthday...and that you are going to guess it. - Have them take the month number from their birthday:
January = 1, Feb = 2 etc. - Multiply that by 5
- Then add 6
- Then multiply that total by 4
- Then add 9
- Then multiply this total by 5 once again
- Have them add to that total the day they were born on. If they were born on the 18th, they add 18, etc.
- Have them give you the total. In your head, subtract 165, and you will have the month and day they were born on!
How It Works: Let M be the month number and D will be the day number. After the seven steps the expression for their calculation is:5 (4 (5 M + 6 ) + 9 ) + D = 100 M + D + 165 Thus, if you subtract off the 165, what will remain will be the month in hundreds plus the day! That's Pretty Cool Math Stuff!
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