No diagram is given. This is from revision exercise in RD Sharma. What is the other possible diagram for this question? is there any difference between circumference and perimeter of semi-circle? (i thought circumference is πr nd perimeter is πr+2r, am i right?)

Asked by Divyaa | 28th Mar, 2017, 09:22: AM

Expert Answer:

Hi Divya,
 
You can refer to the link below for the solution. However the answers still do not match. This is cause for this kind of a problem a diagram is needed otherwise there are many possibilities.
 
http://www.topperlearning.com/study/cbse/class-10/mathematics/text-book-solutions/r-d-sharma-mathematics/42/areas-related-to-circles/286/b101c2s3e9#show-question-69581
 
I have given you one diagram in the previous query. The other one would be :
 
 
Not just this. There is still yet another diagram. I am sending you another link from ICSE Selina textbook, where a similar kind of problem is there only there the diameter is given instead of the circumference. However, there they have given a figure, which most students or experts would not have into consideration since the question is not framed correctly.
 
Still I am sending you the link in case you want to go through the third type of figure possible.
 
http://www.topperlearning.com/study/icse/class-10/mathematics/text-book-solutions/selina-concise-mathematics-part-ii/407/circumference-and-area-of-a-circle/1035/b110c2s3e9#show-question-199525
 
It is Q. 10 from Ex 21 (C) of the chapter Circumference and Area of a Circle. I suggest you go according to the RD Sharma solution since in the ICSE question they had provided the diagram which is yet another possibility and still does not match the question framing.
 
ANSWERS TO YOUR OTHER DOUBTS:
 
Dear Divya, circumference always means the entire boundary of a circle. For a semi-circle we cannot use the term circumference. Instead we can use the term, 
length of the arc of the semi-circle and the diameter together form the perimeter. Or we can always say half of the circumference of a circle. 
 
And yes the perimeter of a semi-circle is always considered with the diameter. So we have to consider the 2r part.
 
Hope this helps you. 

Answered by Rebecca Fernandes | 28th Mar, 2017, 09:51: PM

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