Mot thua ruong hinh chu nhat co chu vi 840m va chieu rong bang 1/2 chieu .
A Tim chieu dai, chieu rong cua thua ruong.
B nguoi ta cay lua o thua ruong, tinh ra cu 100mvuong thu hoach duoc 50kg thoc . Hoi da thu hoach duoc o thua ruong do bao nhieu ra thoc?