Magic Tricks?

Question

Rather than giving a question, I request for some tricks you can do with mathematics. I have a party for my science class and the topic is most likely magic tricks. If you can't think of math, think science. The most surprising trick will definitely get best answer.

Answer 1

how about this
Let a and b be equal non-zero quantities
a = b
Multiply through by a
a^2 = ab
Subtract b2
a^2 − b^2 = ab − b^2
Factor both sides
(a − b)(a + b) = b(a − b)
Divide out (a − b)
a + b = b
Observing that a = b
b + b = b
Combine like terms on the left
2b = b
Divide by the non-zero b
2 = 1

Answer 2

3 men go to a restaurant and had a nice meal costing $25. After eating, all 3 gave the waiter $10 each, so the waiter has to return back $5 and split it into 3 equal parts for the 3 persons which is impossible. So he deciedes to keep $2 for himself and gives back $1 to each person. So technically, each person has paid $9. $9*3 + $2(amount taken by the waiter) = $27+ $2 = $29... but they had paid $30 in all... So where is the missing dollar?

Answer- the meal cost $25, and not $30. The $2 which the waiter kept are already included in the $27 the 3 persons paid. In fact, the $2 should be substracted from the $27 instead of being added to give $25...

Answer 3

How about the ancient Egyptian method of multiplication?

The ancient Egyptians were not aware of the concept of multiplication tables as we are. The following method of multiplying numbers was developed by them to serve their needs.

For example, we will multiply 12 times 8. We all know the answer to this or --do we?

The ancient Egyptians used the following method. Start two columns; one begins with 12, the second begins with 8. The first column will be divided by 2; ignore the remainder; the number in the second column will double with each iteration.

Every place we have an even number in the first column we cross through the numbers in the first and second columns. Then, add the remaining numbers in the second column. This iterative process will work for any pair of positive integers.

½......X2
12......8
..6.....16
..3.....32
..1.....64
.........96


A byproduct of the process is that the number in the first column, in this case 12, is converted to a binary number (base 2) in the following way:
In the first column every place there is an odd number developed in the halving process, replace with 1; for even numbers, replace with 0. Reading from bottom to top we have 1100 which is the binary equivalent of 12.
.

Answer 4

Proof that girls are evil:

girls = time * money

In most cases, time = money, so:

girls = money * money
= money^2

Money is the root of all evil, so:

sqrt(evil) = money
evil = money^2

therefore:

girls = evil

Answer 5

sd d, very interesting calculation... Congratulations.