(1)(230.5+280.5)÷2,
=511÷2,
=255.5(吨);
答:平均每班收聚255.5千克.
(2)(230.5+280.5)÷(48+52),
=511÷100,
=5.11(吨);
答:四年级平均每人收聚5.11千克