Arthur D. answered 05/03/20
Forty Year Educator: Classroom, Summer School, Substitute, Tutor
home plate to 2nd base is 60.5+n where n is the distance from the pitcher's mound to 2nd base
home to first and first to second form a right triangle
the hypotenuse is home plate to 2nd base
use the Pythagorean Theorem
(60.5+n)^2=90^2+90^2
3660.25+121n+n^2=8100+8100
n^2+121n+3660.25-16,200=0
n^2+121n-12539.75=0
us the quadratic formula
(-121±√(14641+50159)/2
(-121±√64800)/2
(-121+254.55844)/2
133.55844/2
66.779≈66.8 feet