Question

The numbers 1, 2, ... ,10 are to be entered into the 10 boxes shown below, so that each number is used exactly once: P = (\square + \square + \square + \square + \square)(\square + \square + \square + \square + \square). What is the maximum value of P? What is the minimum value of P?

Answer 1

Maximum: 756

Minimum: 600

Explanation:

A square is the shape that has the maximum area out of all possible rectangles of a given perimeter. This means that to create the maximum value of P, you will want the two parentheses to be as close in value as possible, and to create the minimum value, for them to have the biggest difference. 1+2+3...+10=55, which is not even, but can be divided as closely as possible into 27 and 28, which have a product of 756. This can be done in this problem in several ways, one of which is:

(1+3+5+8+10)(2+4+6+7+9)

For the minimum, the largest difference can be made when one term is full of the smallest numbers, and the other is full of the largest, or:

(1+2+3+4+5)(6+7+8+9+10)=600

Hope this helps!