Composite Area Help

scwatson13

New member
Joined
Apr 11, 2019
Messages
1
Hi,

I am having trouble completing different composite area problems. It seems like I know the formulas but then I don’t get the right answer. I have been using problems where I have an answer key so I can see if I’m solving them correctly. If you can help me, I would really appreciate it. Thanks!
 

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Jomo

Elite Member
Joined
Dec 30, 2014
Messages
3,351
Hi,

I am having trouble completing different composite area problems. It seems like I know the formulas but then I don’t get the right answer. I have been using problems where I have an answer key so I can see if I’m solving them correctly. If you can help me, I would really appreciate it. Thanks!
You seem to be using the area of a circle but you do not have a circle, you have a semicircle. What is the formula for the area of a semicircle. The area of the rectangle you said is 6*8=72 which of course is not correct. Please try to fix theses error and get back to us with your answer.

OK, that was your work on the lhs.

Now on the right hand side I see that you listed the correct formula for the semicircle but you used 6 for r2. Why is that?
 

Dr.Peterson

Elite Member
Joined
Nov 12, 2017
Messages
3,375
I am having trouble completing different composite area problems. It seems like I know the formulas but then I don’t get the right answer. I have been using problems where I have an answer key so I can see if I’m solving them correctly. If you can help me, I would really appreciate it. Thanks!
One problem is that your work is quite disorganized, with a mix of right and wrong bits of work, and no labeling.

If you want to be able to both check over your work, and have someone else comment on it, you need to write things like this:
  • Rectangle: L = 8 m, W = 6 m, area = LW = 8*6 = 48 m^2
  • Semicircle: radius r = 3 m, area of circle = pi r^2 = 3.14*3^2 = ...; half of that = ...
  • Total: ...
When you label what you are doing, everything works better, because you can see whether you really did what you claimed to be doing. It also helps if you can get rid of the parts you know are wrong, so that you (and we) don't get confused.
 
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