Question

David swimming pool is 28 feet long and 21 feet wide how many feet does David to save by swimming diagonally across the pool instead of swimming the length and then the width of the pool

Answer 1

If he swan the length and the width of the pool  it would be 21 x28 = 588 sq ft.
by swimming the length and the diagonal of the pool (25 ft)  found that by using the pythagorean therom      so now you are multiplying 21 x 25 = 525   

588-525= 63 ft   he is saving