Magic or Math

Trick no:1

Iam 100% sure this trick will impress you

*Think of a number.
*Double it.
*Add 10.
*Halve it.
*Take away you original number.
*Is your answer 5?
Try this with a different starting number. Did you get a different result? Why does this happen?
Write the answer on a piece of paper without letting anybody see it and seal it in an envelope. Have somebody hold the envelope and at the end ask them to open it and reveal the number you wrote at the beginning. Wow, Magic!

Trick no :2

*Write down your age.

*Multiply it by 1/5 of 100.

*Add on today's date (e.g. 2 if it's the 2nd of the month).

*Multiply by 20% of 25.

*Now add your shoe size (if it's a half size round to a whole number).

*So Finally subtract 5 times today's date.

*Show me your final answer!

Look at the answer, the hundreds are the age and the remaining digits are the shoe size. If for instance somebody shows you 1105, there are 11 hundreds - the age, and the remaining digits 05 (or 5) show the shoe size.

Now, how on earth does that work?