How to Guess the Day of the Week Your Friend Was Born

If you have some friends born between 1900 and 2000, then maybe you can impress them with this trick: find the day of the week that they were born.

Here are the steps:

(1) Let $y$ be the year of their birth. Evaluate $\frac{y - 1}{4}$ and ignore the remainder. For example, we want to know the date March 3, 1947, then we have

$\displaystyle \frac{1947 - 1}{4} = \frac{1946}{4} = 486$.

(2) Find what day of the year is the date and let’s represent it D. There are 31 days in January, 28 days in February, and March 3 is the third day.

$D = 31 + 28 + 3 = 62$

(3) Let $s = y$ + the result in (1) + $D$.

$s = 1947 + 486 + 62 = 2495$

4.) Divide $s$ by $7$ and get the remainder.

$\frac{2495}{7} = 356$ remainder $3$.

Now, you can guess the day of the week using the remainder.

Remainder: Day

0: Friday
1: Saturday
2: Sunday
3: Monday
4: Tuesday
5: Wednesday
6: Thursday

Hence, March 3, 1947 is a Monday.

Source: Nature of Mathematics

The Loop Game: Pool in Elliptical Table

Mathematics enthusiast and author Allex Bellos has created an elliptical pool table and he named it “The Loop Game.” It was supposed to always make the ball go to the table pocket. This can be done by placing the pocket at one of the foci and hitting the ball placed on the other focus. This is easy to say theoretically, but of course in playing, you also have to consider Physics.

Watch the video of one of the newest interesting games that uses mathematics in real life.

To those who are interested about ellipse, he has an explanation about in his book “The Grapes of Math: How Life Reflects Numbers and Numbers Reflect Life.”

You can find the website of the game here and watch extra footage in Youtube here.

Practice Solving Equations with Equate Board Game

If you want your children or students practice equations and operations, you might want to try Equate: The Equation Thinking Game. Equate is a math board game that works like Scrabble. In Equate, instead of forming words, you can form equations. Younger children can choose an easy game which only consists of addition and subtraction, while older children can include multiplication and subtraction. Even more challenging is to include fractions!

Just like Scrabble, you can have double or triple scores in Equate. This can make players think of equations that yields a larger answers, while practicing their arithmetic.

Equate can be played 2-4 players ages 8 years old and above.

Although this game is challenging, it could also take a while to finish one game. Games which include fraction is expected to last up to 120 minutes.