题干

如图,将一张正方形纸片的4个角剪去4个大小一样的小正方形,然后折起来就可以制成一个无盖的长方体纸盒,设这个正方形纸片的边长为a,这个无盖的长方体盒子高为h.

(1)若a=18cm,h=4cm,则这个无盖长方体盒子的底面面积为                                 

(2)用含a和h的代数式表示这个无盖长方体盒子的容积V=​                                

(3)若a=18cm,试探究:当h越大,无盖长方体盒子的容积V就越大吗?请举例说明;这个无盖长方体盒子的最大容积是​                                ​.

上一题 下一题 0.0难度 选择题 更新时间:2019-03-04 11:37:29

答案(点此获取答案解析)

解:(1)∵a=18cm,h=4cm,∴这个无盖长方体盒子的底面面积为:(a﹣2h)(a﹣2h)=(18﹣2×4)×(18﹣2×4)=100(cm2);故答案为:100cm2;(2)这个无盖长方体盒子的容积V=h(a﹣2h)(a﹣2h)=h(a﹣2h)2(cm3);故答案为:h(a﹣2h)2cm3;(3)若a=18cm,当h越大,无盖长方体盒子的容积V不一定就越大,∵V=h(

同类题4

完形填空

    Alice was very worried about her dad. For some time now she had noticed he was 1 his hair. One day, she asked him, “Daddy, every day you have less hair.2 is that?” Her father smiled and said, “It's the hair thief. He visits my head during the night when I'm 3. One by one he 4 out my hair, as much as he likes.”

    This worried Alice but she was 5 to help her father. That very night she stayed 6 as long as she could. When she was 7 her dad and mom had fallen asleep, she took a hammer and went straight to their bedroom. She walked carefully in order not to make any 8. She didn't want the hair thief to hear her. Then she began carefully 9 her father's head. When she arrived at her father's side, she began looking at his head,10to catch the hair thief as soon as he appeared. Before long, she saw a shadow on it and 11 all her strength, she swung the hammer down.

    Thwack! Her father 12a loud cry. The lump(肿块) on his head was big and growing.13 with shock, he turned the light on and saw Alice waving her hammer in the 14 with her hands. “Daddy, I 15 got him. I thought I 16 him, but it looks like he escaped!” said Alice. At the same time, the mother woke up. She 17laughing when she knew what had happened.

    So Alice's father had to 18to her that the hair thief didn't exist, and that losing hair is something that just happens 19 to most daddies. And Alice still worried about her daddy, but she no longer waited for the hair thief.20 , she bought her daddy a very nice sleeping hat.