How far away is second base from home plate on a seventy foot diamond?

Baseball infields are supposed to be square. Therefore, an infield would be 90x90 for Major League Baseball, maybe 40x40 for third graders, and maybe 60x60 for eighth graders. The numbers refer to the distance between bases.

In any case, the formula for calculating the distance from home plate to 2nd base is A Squared + B Squared = C Squared, where A is the distance from home plate to 1st base, B is the distance from 1st base to 2nd base, and C is the distance from home plate to 2nd base.

This sounds like your league has an infield of 50x50. Using the formula above, the distance from home plate to 2nd base would be 70.71 feet, which comes out to 70 feet and 8.5 inches. Your league probably just defines it as 70 feet for simplicity in measuring, thus resulting in the term 50x70.