Question

How many cubic yards in 4" x 2500sq ft?

Answer 1

4" x 2500 ft², namely 4 ft x 2500 ft², will just be 4*2500*ft*ft², or 10000 ft³.

$\bf \begin{array}{ll} yd&3ft\\\\ (yd)^2&(3ft)^2\\ &(3^2ft^2)\\ &9ft^2\\\\ (yd)^3&(3ft)^3\\ &(3^3ft^3)\\ &27ft^3 \end{array}$

since there are 27 ft³ in 1 yd³, then how many yd³ are there in 10000 ft³?

10000/27, that many yd³.