American football fields measures 100 yds long between the end zones and are 53 1/3 yds wide. is the length of the diagonal across this field more or less than 200 yds?

So basically, the football field is 100 by 53 1/3.
Since you are looking for the diagonal, use the Pythagorean Theorem.

a^2+b^2= c^2

c will represent the diagonal, or hypotenuse.

a^2 + b^2 = c^2

100^2 + 53 1/3^2 = c^2

10000 + 2844.4 = c^2

12844.4 = c^2

= c

c = 113.3 yards

The diagonal is less than 200 yards.