Your Own Mathematics Puzzle

Impress your friends with this cool mathematics puzzle. (and know how maths is useful in real life)

This lets you give the age of a person and the number of siblings in their family.

Questions that you need to ask

1. Think of your age in years 
2. Multiply your age by 2
3. Add 10
4. Multiply by 5
5. Add number of siblings that you have
6. Subtract 50 from this number
7. What's the number?

How it Works

If you know an animal called Algebra, this would be a cakewalk for you. How it works is this. Follow the questions....

Question                     Answer Example       Algebraic Equivalent

1. Think of your age in years         15          [10x+y]

2. Multiply your age by 2               30          2[10x+y]

3. Add 10                                       40          2[10x+y] + 10

4. Multiply by 5                              200          5{2[10x+y]+10}=100x+10y+50

5. Add # of siblings you have        203          100x+10y+50+z

6. Subtract 50                               153          [100x+10y+50+z]–50= 100x+10y+z

Prediction: 

You are 15 years old, and you have 3 siblings.

The first two digits on the left (15) give your age, and the rightmost digit (3) gives the number of siblings you have. 

Explanation: 

The algebraic equivalent of the steps result in Step 6, which is 100x + 10y + z, where z<10. But 100x + 10y + z is the algebraic equivalent of a three-digit number, with the digits in the hundreds and tens places giving the age, and the digit in the ones place giving the number of persons in the house. (Note: the number of siblings has to be less than 10, otherwise this “trick” will not work.)