Puzzle Details

If I give you seven apples, you will then have five times as many as I would then have, however, if you give me seven apples, we will then both have the same number of apples. How many apples do I currently have?

Answer: I have 14 apples and you have 28 apples.

We can easily work this out with a little algebra. I have A apples and you have B apples, then

5 x (A - 7) = B + 7    [1]

A + 7 = B - 7    [2]

From [1] we have:

5A - 35 = B + 7
5A = B + 42   [3]

From [2] we have:

A + 14 = B        [4]

We can then use [4] in [3] to give:

5A = (A + 14) + 42
5A = A + 56
4A = 56
A = 14

Which gives B = 28 (by [4]).

My Favourite Illusions

 Shadow Illusion Are the squares A and B the same colour? Spinning Dancer Which way is the dancer spinning? Impossible Waterfall? Is the water flowing uphill in this impossible waterfall? The Butterfly A colourful butterfly?
 Duck Or Rabbit? Is this a duck or a rabbit? Hidden Faces Can you find his three daughters as well? Blind Spot An amazing demonstration of your blind spot. Impossible Prongs? Impossible prongs?
 What Am I? Can you tell what this is a picture of? Who Turned To? Who is missing? Same Eyes? Are her eyes the same colour? Parallel Cafe Wall Lines? Are the horizontal lines parallel?