Semicircle

Geometry Level 2

What is the perimeter of a semicircle with radius 7?

Use the approximation $\pi \approx 22/7$ .

The answer is 36.

23 solutions

Niranjan Khanderia
Oct 8, 2014

The curved part is $\pi\cdot r =22$ while the straight diameter is 14, for a total of 36.

A clever question. I calculated the Circumfrence as 2 pi r/2 but did not realise that you have to add the diameter to the perimeter.

Gk Sharma - 6 years, 8 months ago

can you help me to understand the cone and the cylinder (BSc)? please

Amisha Mhatre - 6 years, 8 months ago

You take a round pencil cut off both ends flat. That is a cylinder . Its volume is , $V=\pi*r^2*h.....r,~ the~radius~and ~h~the~height.$
When you sharpen a pencil, the sloping portion with the tip is a cone upside down. A cone will have a circular base, sloping sides ending in a point. Its volume is 1/3 that of the cylinder with same r and h. Remember the ice cream cone ?

Niranjan Khanderia - 6 years, 8 months ago

if i solve your problem! what will you give me?

Abbas Bhai - 6 years, 7 months ago

That's easy, I might not be able to explain well but this will help http://www.virtualnerd.com/tutorials/?id=PreAlg 11 03 0011 & http://math.about.com/od/formulas/ss/surfaceareavol 3.htm

Kushagra Arora - 6 years, 7 months ago

Me too, I guess I made a slight oversight in high school.

Simphiwe Ciliza - 6 years, 7 months ago

the perimeter of the circle is 2(pi)r, when you are finding the perimeter of the semicircle, you just divide it by two.. where did you get that???????????????

Paolo Trace Perez - 6 years, 8 months ago

The outside perimeter =pi x r = 22, then you have to add in the straight line (the diameter) which = r x 2 = 14, then 22 + 14 = 36

Julian Blatt - 6 years, 8 months ago

the length of a semi circle is πr. But the perimeter of a semi circle also includes the diameter which is 2r. Therefore the perimeter of a semi circle = πr + 2r = r(π + 2)=[7{(22/7)+2}]=36.............this is the formula for getting perimeter of semicircle.......r=radius, pi=22/7;

anindita pal - 6 years, 8 months ago

perimeter = πr + 2r =22/7x7+14=36

Dora Silva - 6 years, 8 months ago

A nicer, and much more accurate, approximation for pi is 3+1/(7+1/16).

Anthony Cutler - 1 year, 11 months ago

Mohamed Abo-El Fadl
Nov 3, 2014

Total perimeter = Curved area + Diameter = Pi*r + 2r = 22+14 = 36

Edwin Gray
Feb 7, 2018

C = 2 pi r, so C/2 = Pi r = (22/7) 7 = 22. Adding the diameter = 2r = 14, the sum = 36. Ed Gray

Ahmad Ali
Nov 21, 2014

find the circumference of this Circle having radius 7, and then divided by 2 and you will obtained the lenght of curve Path Add it the Diameter of this circle you can find the Total Lenght of this perimeter.

Ahmed Obaiedallah
Jan 21, 2016

Don't forget to add the diameter length $P=\pi\cdot r+2r=(\pi+2)r=36$

Vishal S
Dec 16, 2014

Perimeter of a semicircle is given by P=2(pi)r/2+2r

by substituting the given values, we get P=2(22/7)7/2+2(7)=36

Md Moniruzzaman
Nov 22, 2014

πr+d= 22/7*7+14=36

Sree Vidya
Nov 4, 2014

pi*r is the half circle perimeter + we have a diameter of 14 that results to 36 :)

Syed Gilani
Nov 3, 2014

(2 pi r)/2 = the circumference of the semi-circle but we need full perimeter so also add the diameter hence D= 2*r = 14 now 3.14x7 = 22 + 14 = 36

Roe Biñas
Nov 3, 2014

p=(2pi r/2)+2r= [[2(3.14)(7)]/2]+(2X7) p=21.98+14 p=35.98 p=36

Aniruddha Banerjee
Nov 3, 2014

(2 pi r/2)+2r=36

Gau Sin
Nov 3, 2014

it should be 22units.because when talking about semicircle it does not include the diametrical part .so the question should be find perimeter of the figure...........