The number of pear trees in the orchard is more than 250 and less than 300, and they can be arranged in 18 or 27 rows. Do you know how many pear trees there are in the orchard? Explain why.
果园里的梨树的棵数比250棵多，比300棵少，它们正好可以排成18排或27排．你知道果园里的梨树究竟有多少棵吗？说明理由．
<result>270</result>