Cho lăng trụ
có thể tích bằng
. Gọi
,
lần lượt là hai điểm nằm trên hai cạnh
và
sao cho
là trung điểm của
và
. Đường thẳng
cắt đường thẳng
tại
và đường thẳng
cắt đường thẳng
tại
. Thể tích khối đa diện lồi
bằng
![img1](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img5.png)
![img6](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img6.png)
![img7](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img7.png)
![img8](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img8.png)
![img9](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img9.png)
![img10](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img10.png)
![img11](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img11.png)
![img12](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img12.png)
![img13](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img13.png)
![img14](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img14.png)
![img15](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img15.png)
![img16](https://cungthi.online/upload/questionbank3/eduquestion/2019321164257868732/obj2019321164257868732246388_images/obj2019321164257868732246388_img16.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:B
Lời giải:
Phân tích: Ta có:
.
Mặt khác:
. Vậy
. Chú ý chỗ
có thể tính cách khác như sau:
Ta có:
. Lại có:
.
Đáp án đúng là B