Cho tứ diện
,
và
là các điểm thuộc các cạnh
và
sao cho
,
,
là mặt phẳng qua
và song song với
. Kí hiệu
và
là các khối đa diện có được khi chia khối tứ diện
bởi mặt phẳng
, trong đó,
chứa điểm
,
chứa điểm
;
và
lần lượt là thể tích của
và
. Tính tỉ số
.
![img1](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img5.png)
![img6](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img6.png)
![img7](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img7.png)
![img8](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img8.png)
![img9](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img9.png)
![img10](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img10.png)
![img11](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img11.png)
![img12](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img12.png)
![img13](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img13.png)
![img14](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img14.png)
![img15](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img15.png)
![img16](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img16.png)
![img17](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img17.png)
![img18](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img18.png)
![img19](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img19.png)
![img20](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img20.png)
![img21](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img21.png)
![img22](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img22.png)
![img23](https://cungthi.online/upload/questionbank3/eduquestion/20180609588610987028/obj20180609588610987028634232_images/obj20180609588610987028634232_img23.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:A
Lời giải:
Phân tích: Kí hiệu là thể tích khối tứ diện
. Gọi
,
lần lượt là giao điểm của
với các đường thẳng
,
. Ta có
. Khi chia khối
bởi mặt phẳng
, ta được hai khối chóp
và
.
Đáp án đúng là A.