a/b * b/c * c/d * d/e is equal to a/e provided that b, c, d,
and e are not zero
PROVE
a/b * b/c * c/d * d/e
= (a/b *b/c) * (c/d * d/e)
= ab/bc * (c/d * d/e)
= a/c * (c/d * d/e)
= a/c * (cd/de)
= a/c * c/e
= ac/ce
= a/e
Therefore, a/b * b/c * c/d * d/e is equal to a/e provided that
b, c, d, and e are not zero
