Euler found four whole numbers such that the sum of any two of the numbers is a perfect square...
The diagram illustrates the formula: 1 + 3 + 5 + ... + (2n - 1) = n² Use the diagram to show that any odd number is the difference of two squares.
How much peel does an apple have?
First the fire :
If, just as a first approximation, we don't worry about a filled
bucket being heavier to carry, what is the best point on the river
bank for the fire-fighter to fill the bucket ?.
If you need to do a calculation with lengths, what measurements
will you need to make from your diagram ?
It's a general solution you are looking for, so you may need two
or three different arrangements or diagrams to see how the solution
relates to the positions of the fire-fighter and the fire.
Now the keys :
Draw a horizontal line. Fix two pins at different horizontal
levels above the line. A set of keys slides on a string and the
string runs over those two pins (the pins are not directly
underneath one another). Gradually let out the string length until
the weight of the keys brings the string down to touch the drawn
Can you see the connection between this problem and the fire
problem above ?