Julian measured the distance around a small fishpond as 27 yards. which would be a good estimate for the distance across the pond, 14 yards, 9 yards, or 7 yards?

9 yards.

I'm assuming that the small fishpond is a circle.  The circumference of a circle (the distance around) is equal to 2πr, or πd, pi times the diameter (the distance across).  Pi is appromately 3.14, so we can divide 27 by about 3 to get 9 yards.  This leaves 9 = d, the distance across.

Rational. hope this helps :)