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Answers for Q1
For picture 1
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I have covered very good number of links in this blogs UCEED resource and book collections page for your convenience. To help you with self evaluation and to check - to what extent these concepts really helped you with better understanding, I have decided to share some random sample questions quite often. Hope this self evaluation questions are of great help to you for your preparation :)
Evaluation question 1 :
Given below is a solid in 3D. You need to observe and answer the following (try to answer these questions without putting pen on paper !)
- How many straight lines are used to form the solid ?
- How many surfaces are there ?
- How many rectangles, squares and other shapes are there ?
- How many sharp edges (corners or points) are there in the picture ?
Picture source : JMCinTyre
Now the same image is manipulated and is sectioned (cut) at the specified mark. Now, what will be the answers for the above same set of 4 questions ? try to imagine and answer without the use of pen/pencil.
Watch out for more practice questions !
Answers for Q1
For picture 1
- No. of straight lines used to form the shape in the first picture = 29
- No. of surfaces = 12
- No. of rectangles that is directly visible = 7; No. of squares = 0 (thanks to Advait Bharath for pointing out earlier mistake)
- No. of sharp edges (corners) = 19
For sectioned picture
- No. of straight lines used to form the shape in the first picture = 21
- No. of surfaces = 10
- No. of rectangles that is directly visible = 4; No. of squares = 1
- No. of sharp edges (corners) = 16
Hope you got the same answers
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can you give the answers so we can cross check?
ReplyDeletewill give soon
Deletemy answer for q1 1st part is coming 28.please check
ReplyDeleteYa, u r r8, it's 28! thanks
Deleteno sir its 29
Delete29?sir.
DeleteIt's 28 friends, I have checked, probably you are counting one of the same line twice, please check
Deleteya 28 is correct
DeleteSir even I'm getting 29
Deleteok, my mistake, its 28.
ReplyDeleteit is 28, it's ok, np, I could tell you where the mistake might have happened, if you need explanation, I can make a pic and explain in free time.
Deletesir , in this ques we have to find no of squares and rectangle. right? now my ques is when the image is sectioned at the mark..then i dont find any square in the image(visible). but at the same time i know there is one square formed at the back but that in not visible.i got confused in these type of questions..whether we have to find the visible one or those which are not visible too..hope you got my point..
ReplyDeleteThe question is to find the surface shapes (squares, rect etc) count for the solid formed formed after the cut was done. It's not only for the visible ones but for the whole solid after the cut.
DeleteSir can u plz explain this question. i m getting confused . in this ques we have to find rectangles and squares .but in the first part ..i can only see 4 rectangles (visible) including the bottom..rectangle should be of 4 side and must be closed. but i dont find anything like that..may be i m confused and mistaken. ..plz elaborate the answer if possible
ReplyDeletewell, the total is 6 rectangles, observe the right most rectangle with dimension 59, and the landing/projecction 19 height. On the left side, there are three (including the one rectangle as appears from top view). And finally bottom rectangle that you already considered. I considered the slant surface (with dimension 59 in it) as square. You may check my post on 'counting number of faces on geo objects' for better understanding. All you need is observe and perceive geo shapes.
DeleteSir, The slanting shape is NOT A SQUARE!!!!!!!
ReplyDelete(Apply Pythagoras theorem)
Ya Advait, I noted that mistake yesterday itself when replying to previous comment, that's why I mentioned "I considered ...." in my previous comment instead of "slant portion is square"....anyway thank you, I will correct it :)
DeleteSir, In the ques where we need to find out squares and rectangles in sectioned cut, is the slant portion the square? If yes, how can we say it coz we don't know the dimensions of the slant portion and we don't know how far is the cut made? In that case the answer should be can't be determined.
ReplyDeleteI already pointed this in me earlier comments. Since the picture dimensions are not given, I just CONSIDERED it as square. It's ok, you can either consider them as rectangle or square, but the thing is whether are you able to identify the surface or not. That is important. In exams, they will give you good details for such questions. Don't worry!
DeleteFor faces i am getting 12 faces os it right
ReplyDeleteYou better check this to clear your doubt
DeleteSolving number of faces on geometrical solids
Sir Euler's formula states that
ReplyDeleteF+V=E+2
according to which the 2nd question doesn't sum up
no of edges should be 24
Yep no. of straight lines in second question should be 24. (28-4)
DeleteHey can u pls get me the solutions of q1 or explain. Getting very doubtfull
ReplyDeleteit's already up there dude, u can also chk the following
Deletehttp://stuffyoulook.blogspot.com/2013/09/solving-number-of-faces-on-solid.html
http://stuffyoulook.blogspot.com/2013/09/solving-tetrahedran-tessellation-problem.html
http://stuffyoulook.blogspot.com/2016/01/3D-solid-manipulations-and-unfolding-of-shapes.html