Có thể chia khối lập phương
thành bao nhiêu khối tứ diện bằng nhau mà mỗi tứ diện có bốn đỉnh thuộc tập các điểm
? A. Sáu B. Vô số C. Hai D. Bốn Đáp án và lời giải Đáp án:A Lời giải: + Chia khối lập phương
thành 2 khối lăng trụ bằng nhau
và
+ Xét khối lăng trụ
và nối các đường như hình vẽ sau đây Hai khối tứ diện
bằng nhau vì chúng đối xứng với nhau qua mặt phẳng
Hai khối tứ diện
bằng nhau vì chúng đối xứng với nhau qua mặt phẳng
Như vậy khối lăng trụ
được chia thành 3 khối tứ diện
bằng nhau. + Làm tương tự như vậy với khối lăng trụ
ta cũng chia được 3 khối tứ diện bằng nhau. + Vậy, ta có thể chia khối lập phương thành 6 khối tứ diện bằng nhau.
Câu hỏi thuộc đề thi sau. Bạn có muốn thi thử?
Bài tập trắc nghiệm số 2 về lý thuyết khối đa diện - hình học lớp 12 chuyên đề khối đa diện [ có lời giải chi tiết ] Làm bài
Chia sẻ
Một số câu hỏi khác cùng bài thi.
- Cho bốn hình sau đây. Mệnh đề nào sau đây sai .
- Hình đa diện trong hình vẽ có bao nhiêu mặt?
- Cho một bát diện đều. Các khẳng định đúng là. 1. Bát diện đều có đúng 12 cạnh 2. Bát diện đều có đúng 8 đỉnh 3. Bát diện đều nếu có cạnh bằng a thì sẽ nội tiếp một mặt cầu có bán kính bằng
4. Ghép hai khối tứ diện đều ta được một khối bát giác đều
- Tìm mệnh đề đúng trong các mệnh đề sau
- Hình vuông có mấy trục đối xứng?
- Trong các mệnh đề sau đây, mệnh đề nào sai ?
- Khối đa diện loại {3;4} là khối có .
- Hình chóp tứ giác đều có số mặt phẳng đối xứng là.
- Trong các khẳng định sau, khẳng định nào đúng ?
- Vật thể nào trong các vật thể sau không phải là khối đa diện.
- Số đỉnh của một hình bát diện đều là ?
- Trong các hình dưới đây, hình nào là khối đa diện?
- Cho một hình đa diện. Tìm khẳng định sai trong các khẳng định sau.
- Hình nào dưới đây không phải là hình đa diện?
Hình 1
Hình 2
Hình 3
Hình 4
- Trong hình bát diện đều số cạnh gấp mấy lần số đỉnh.
- Mỗi đỉnh của bát diện đều là đỉnh chung của bao nhiêu cạnh ?
- Khối đa diện đều loại
có tên gọi là.
- Trong các mệnh đề sau, hãy chọn mệnh đề đúng. Trong một khối đa diện thì.
- Nếu ba kích thước của một khối chữ nhật tăng lên 4 lần thì thể tích của nó tăng lên.
- Cho khối chóp
có đáy là hình bình hành.Mặt phẳng [SAC] chia khối chóp S.ABCD thành mấy khối tứ diện.
- Hình bát diện đều có bao nhiêu mặt phẳng đối xứng
- Có thể chia khối lập phương
thành bao nhiêu khối tứ diện bằng nhau mà mỗi tứ diện có bốn đỉnh thuộc tập các điểm
?
- Thể tích của khối đa diện tạo bởi hình sau là.
- Cho khối tứ diện
. Lấy một điểm M nằm giữa A và B, một điểm N nằm giữa C và
Bằng hai mặt phẳng
và
ta chia khối tứ diện đã cho thành 4 khối tứ diện.
- Cho hình chóp S.ABCD đáy ABCD là hình thang vuông tại A, B, AB=BC=a, AD=2a;
. Nhận định nào sau đây đúng
Một số câu hỏi khác có thể bạn quan tâm.
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answers:
All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals - whether marsupials, platypuses, spiny anteaters, or placental mammals - have in common.But not all animal parents, even those thattendtheir offspring to the point of hatching or birth, feed their young. Most egg-guarding fish do not, for the simple reason that their young are so much smaller than the parents and eat food that is also much smaller than the food eaten by adults. In reptiles, the crocodile mother protects her young after they have hatched and takes them down to the water, where they will find food, but she does not actually feed them. Few insects feed their young after hatching, but some make other arrangement,provisioningtheir cells and nests with caterpillars and spiders that they have paralyzed with their venom and stored in a state of suspended animation so that their larvae might have a supply of fresh food when they hatch.
For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them anedgein their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size thatitis better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young areshieldedagainst the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.
Question: The word "provisioning" in the second paragraph is closest in meaning to _______.
Khi nói về dao động cưỡng bức, phát biểu nào sau đây sai?
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answers:
All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals-- whether marsupials, platypuses, spiny anteaters, or placental mammals -- have in common.But not all animal parents, even those thattendtheir offspring to the point of hatching or birth, feed their young. Most egg-guarding fish do not, for the simple reason that their young are so much smaller than the parents and eat food that is also much smaller than the food eaten by adults. In reptiles, the crocodile mother protects her young after they have hatched and takes them down to the water, where they will find food, but she does not actually feed them. Few insects feed their young after hatching, but some make other arrangement,provisioningtheir cells and nests with caterpillars and spiders that they have paralyzed with their venom and stored in a state of suspended animation so that their larvae might have a supply of fresh food when they hatch.
For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them anedgein their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size thatitis better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young areshieldedagainst the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.
Question: The word "tend" in the second paragraph is closest in meaning to _______.
Phát biểu nào sau đây về dao động tắt dần là sai?
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answers:
All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals - whether marsupials, platypuses, spiny anteaters, or placental mammals - have in common.But not all animal parents, even those thattendtheir offspring to the point of hatching or birth, feed their young. Most egg-guarding fish do not, for the simple reason that their young are so much smaller than the parents and eat food that is also much smaller than the food eaten by adults. In reptiles, the crocodile mother protects her young after they have hatched and takes them down to the water, where they will find food, but she does not actually feed them. Few insects feed their young after hatching, but some make other arrangement,provisioningtheir cells and nests with caterpillars and spiders that they have paralyzed with their venom and stored in a state of suspended animation so that their larvae might have a supply of fresh food when they hatch.
For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them anedgein their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size thatitis better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young areshieldedagainst the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.
Question: The word "edge" in the third paragraph is closest in meaning to _______.
Khi nói về dao động cưỡng bức, phát biểu nào sau đây làđúng?
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answers:
All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals - whether marsupials, platypuses, spiny anteaters, or placental mammals - have in common.But not all animal parents, even those thattendtheir offspring to the point of hatching or birth, feed their young. Most egg-guarding fish do not, for the simple reason that their young are so much smaller than the parents and eat food that is also much smaller than the food eaten by adults. In reptiles, the crocodile mother protects her young after they have hatched and takes them down to the water, where they will find food, but she does not actually feed them. Few insects feed their young after hatching, but some make other arrangement,provisioningtheir cells and nests with caterpillars and spiders that they have paralyzed with their venom and stored in a state of suspended animation so that their larvae might have a supply of fresh food when they hatch.
For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them anedgein their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size thatitis better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young areshieldedagainst the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.
Question: According to the passage, how do some insects make sure their young have food?
Một vật dao động cưởng bức dưới tác dụng của ngoại lực F = F0cos[0,5πft] [với F0 và f không đổi. t tính bằng s]. Tần số của dao động cưỡng bức của vật là ?
Chọn đáp án sai khi nói về dao động cưỡng bức:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
ACADEMICS ARENT THE PROBLEM
Studies about how students use their time might shed light on whether they face increased academic and financial pressures compared with earlier eras.
Based on data about how students are spending time, academic or financial pressures dont seem to be greater now than a generation ago.
The data show that full-time students in all types of colleges study much less now than they did a generation ago - a full 10 hours a week less. Students are also receiving significantly higher grades. So it appears that academic pressures are, in fact, considerably lower than they used to be.
The time-use data dont suggest that students feel greater financial pressures, either. When the time savings and lower opportunity costs are factored in, college appears less expensive for most students than it was in the 1960s. And though there are now full-time students working to pay while in college, they study less even when paid work choices are held constantly.
In other words, full-time students do not appear to be studying less in order to work more. They appear to be studying less and spending the extra time on leisure activities or fun. It seems hard to imagine that students feeling increased financial pressures would respond by taking more leisure.
Based on how students are spending their time then, it doesnt look as though academic or financial pressures are greater now than a generation ago. The time-use data dont speak directly to social pressures, and it may well be that these have become more intense lately.
In one recent set of data, students reported spending more than 23 hours per week either socializing with friends or playing on the computer for fun. Social activities, in person or on computer, would seem to have become the majorfocusof campus life. It is hard to tell what kinds of pressures would be associated with this change.
Question: Students get higher grades as _______.