Lesson 21 Listen and say Look at the numbers on the blackboard: 50, 60, ____, ____, 90. 看黑板上的这些数字：50, 60, ____, ____, 90. Who can guess the missing numbers? 谁能猜到空缺处的数字？ It's easy. Fifty plus ten is sixty. So the missing numbers are seventy and eighty. 很简单。五十加十是六十。所以空缺的数字是七十和八十。 One hundred minus ten is ninety. 一百减去十是九十。 Ninety minus ten is eighty. 九十减去十是八十。 So the missing numbers are eighty and seventy. 所以空缺处的数字是八十和七十。 Well done. 做得好。 Listen,look, and learn Fifty plus ten is sixty. One hundred minus ten is ninety. 五十加十是六十。一百减去十是九十。 Forty plus twenty is sixty. Seventy plus ten is eighty. 四十加二十是六十。七十加十是八十。 Read and write A plus B is 100. A minus B is 20. A加上B 是100. A减去B是20. A is ______, B is ______. A是 ______, B 是 ______. A plus B is 90. A minus B is 50. A加上B 是90. A减去B是50. A is ______, B is ______. A是 ______, B 是 ______. A plus B is 70. A minus B is 10. A加上B 是70. A减去B是10. A is ______, B is ______. A是 ______, B 是 ______. |
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