问题 解答题

下面哪些算式运用了加法运算定律?分别运用了哪些运算定律?

38+78=48+68

31+67+19=31+19+67

119+81+42=(119+81)+42

117+45+83+55=(117+83)+(45+55)

答案

①38+78=48+68,没运用加法运算定律;

②31+67+19=31+19+67,运用了加法交换律;

③119+81+42=(119+81)+42,运用了加法结合律;

④117+45+83+55=(117+83)+(45+55),运用了加法交换律与结合律.

阅读理解

阅读理解

      Dave and Bob like playing very much. They often came up to the city from the country on Sundays to do some shopping, had a meal and then went to the theatre in the evening.    

      One evening it was twenty-five past eight and they were waiting for the play to begin. The theatre was  full. Everyone was laughing, talking and eating something. Soon the red curtain(幕) went slowly up, the       lights in the theatre went out(熄灭 ) and the play began. Then everyone was quiet. They watched, listened and thought. But it was a sad play. Dave and Bob didn't like it.      

      Last Sunday they saw a happy one and liked it. After the play Dave and Bob took the last train to        leave the city at ten past twelve.

1. Dave and Bob often went to         .    

A. the city from the village on Saturdays    

B. the country from the town on Sundays    

C. the city from the country on Sundays    

D. the theatre from the shop on Sundays

2. They went to the theatre in the evening        .    

A. before they did some shopping    

B. after they had a meal    

C. before they had a meal    

D. in the country

3. The theatre is full of          .  

A. talking              

B. laughing    

C. eating                

D. people

4. When the lights in the theatre went out,the people         .    

A. were quiet            

B. stood up    

C. began to talk          

D. went out of the theatre

5. They enjoyed going        .    

A. to the theatre to see a happy play    

B. to the theatre to see a sad play    

C. to the country to do some shopping    

D. to the country to have a meal

填空题