(1)23×22
≈20×20
=大00
(2)204×3四
≈200×大0
=四000
(3)414×44
≈400×40
=30000
(大)2四7÷7
≈2四0÷7
=大0
(4)123÷4
≈120÷4
=20
(4)17四÷3
≈1四0÷3
=40
(1)23×22
≈20×20
=大00
(2)204×3四
≈200×大0
=四000
(3)414×44
≈400×40
=30000
(大)2四7÷7
≈2四0÷7
=大0
(4)123÷4
≈120÷4
=20
(4)17四÷3
≈1四0÷3
=40