Try this simple method, in only 3 calculations to get the answer. We used this in my office 65 years ago when we were calculating the area of a cross section of a tube. So imagine that your drawing is a tube. FORMULA = o/d minus gauge X Pi X gauge. o/d is the outside diameter of the tube. The gauge is what we called the thickness of the wall of the tube. So in your example the o/d would be 120 cm and the thickness would be 30 cm. So 120 minus 30 x Pi (3.14) x 30 = Answer 8478 sq. cm. So let me know what you think.
I think I love it and will spend some time with it. Sorry this is such a late comment on such a thoughtful and interesting one. I am just figuring out how to work back through comments. I love the applications from people who actually use this. I farm, and so much of the math I teach, I also use, but very few kids see the point from textbook examples. Your comment gets to the point of why we need to learn this and how it is applied in the real world.
@@danielschaben We used this method to find the strength of tubes. The tubes were made of aluminium alloy. The tubes were for fuel pipes in aircraft, irrigation pipes, scaffold poles and a 1000 and one other uses. They were made in various alloys depending on their application, so they were of various strengths depending on what they were to be used for. They were made to British Standards and Aircraft specifications, requiring a minimum strength in tons per sq. inch. So you needed to know the area of the cross section of the tube. The tube was tested to breaking point in a Tensile Testing machine. The breaking point in tons was then calculated per sq. inch. All these calculations were done on a slide rule, children wouldn't know anything about this nowadays. No calculators then. Hope you find this interesting.
many times the answer is left in terms of pi. This gives the exact answer. multiplying it by 3.14 will only give and approximation. So it really depends on the precision needed. maybe 3.1415 is needed or 22/7.
Question and this is a problem with your method. What abut with decimals? I have a question to work our the shaded area, the larger circle has a radius of 4.1 whereas the smaller one has a radius of 1.7. Now this is where I am having a problem with your method, the answer has to be given to 3 significant figures. Now I can work out the areas of both circles thanks to Pi, however the resulting answer as a whole does not give me the availability to give the answer to 3 significant figures.
(4.1)^2(pi)-(1.7)^2(pi) = 13.92(pi) so now just multiply13.92*3.1415 = 43.72968. So three sig figs would be 43.7. My method works nice so we can eliminate some of the rounding errors that occur by waiting to use the approximated pi until the end.
I'm studying right now and doing a question where the radius of the circles arent given. Only the tangent of the smaller circle where it hits the bigger circle. The distance between those 2 points are given. I have no idea how to do it. Any idea?!?!?
@@danielschaben I just posted a 10 second video of the picture of it, if you want to look at it. I'm not sure if u can use pythagoras but I dont think so. It's in the chapter of trigonometry and the answer is in the back of the book if u want it but it doesnt tell how it's done. Thank you so much!
That's great thank you, I have wrote a story where there is a 700 mile circler area that I guesstimate at 100,000,000 hectares, it is one short story of 6 that I have wrote, and it was just making sure that was right before publishing my book of short stories.
Well.... the bigger circle has to have a radius of 40 and the smaller circle would have to have a radius of 30. Look at your problem again. Are they giving you a diameter or d = 40 on the smaller circle. If that is the case then r = 30 for the larger circle and r = 20 on the smaller circle.
Franchezkaichi Sendou what country are you from? Could you just paste the wording of the problem. I can't get either link to work and probably shouldn't click on links I'm not sure about.
In this case we are using the entire circle, so there is no need to worry about the central angle formed by the two radii. If area of sector is what you need, the do a search for area of sector. The area between two things is BIG AREA - SMALL AREA no matter what shape you deal with.
I don’t understand how you got the answer I thought to work out an area of a circle is radius^ times pie (3.14) and to get the area of the shaded area You minus the area for the smaller circle 60^=3600x3.14=11,304 - 30^=900x3.14=2826 So it’s 11,304 - 2826= 8478 so how did you get the other answer
Thx for this im so bad at this now i know how to answer this kind of Problem But the problem asked to my assignment is the Radius is 7cm and then added more 7cm and the radius is now 14cm
Can you help me please I need the answer a question in general apilites,, we have two circles a one inside the other. The area of the big circle is 36 pi,, what it provided is that there is a short line which measure 2,, it's out from the border of small circle into the bigger one,, where can I send you the photo of it
I think I know it from your description. You know the radius of the big circle is 6. Because the pi*r^2=36 pi. This means that your inner circle has a radius of 4. The area of this circle is 16pi. So the area of the shaded region between them would be 20pi. Because you would subtract them.
@@danielschaben yes yes this is answer,, but the teacher asked if there commen thing between them like a relationship or law that whenever I see a same question can answer it faster (we are supposed to answer every question in 1 min)
For example if once I see the question I know that the big circle area is twice of the small one (I know it's incorrect but Iam giving you an example to understand what I mean with a "faster relationship between them" and that I can do it with all questions with same provided informations
@@user-ok4fv9jq5h square root the area of the bigger without pi sqrt(36)=6, subtract that number from your distance between circles 6-2 =4, square the 4 which is 16. Finally place back the pi and subtract. 36pi -16pi = 20pi
Great question. I'm just leaving pi out of the final calculation. If you take the number multiplied by 3.14 or some other approximation of pi, then you will have an approximate answer. Leaving pi there is just a way to show the exact answer. Now if your question is why is pi in the formula to begin with... well then... that truly is a great question.
Thank you so much, I have a big test today (nwea) and I did NOT know how to do it. This is gonna help me out alot.
lmao what grade did you get
max Wehri nope*
Me too lol
What grade did you get
Your welcome 🙏
This helped, didn't realize it was this easy!
Thanks for the info, helped a lot!
Thanks! I'm helping my son study for a test and this really clear things up.
Glad I could help
that was great thanks
It really helped a lot I was able to complete my work easily and faster than usual.
Hi Mary, see my much simpler formula I have just posted. Let me know how you get on. B.
Thank you that really clarified it for me :)
Nice explanation! I appreciate the help.
Glad it helped!
Thank you a lot...this has helped me so much for my test today. Thanks again😀😊
You're welcome
You are the man. Thank you
You're welcome
Thank you this is one of the last things I need to know for finals
You're welcome
salamat kaayu bay!! nice g
Thanks so much I have been stuck in a question like this for hours
You're welcome 😊
@@danielschaben thanks for helping me with my hw
Thank you so ooo much!!!
You're welcome!
Thanks for this, it really helped me because I'm really BAD at math.......
practice, practice, and then you'll become good at math.😁 thanks for the comment
Thank you so much 😊
keep up the good content
Thanks I will sure try.
👍 thanks you
Thanks
Did you use the pi's??????????
30x30 is 900 but you didn’t multiply the pie with that can someone help me
ahh...!!
thanks for the help☻
Try this simple method, in only 3 calculations to get the answer. We used this in my office 65 years ago when we were calculating the area of a cross section of a tube. So imagine that your drawing is a tube. FORMULA = o/d minus gauge X Pi X gauge.
o/d is the outside diameter of the tube. The gauge is what we called the thickness of the wall of the tube.
So in your example the o/d would be 120 cm and the thickness would be 30 cm.
So 120 minus 30 x Pi (3.14) x 30 = Answer 8478 sq. cm.
So let me know what you think.
I think I love it and will spend some time with it. Sorry this is such a late comment on such a thoughtful and interesting one. I am just figuring out how to work back through comments. I love the applications from people who actually use this. I farm, and so much of the math I teach, I also use, but very few kids see the point from textbook examples. Your comment gets to the point of why we need to learn this and how it is applied in the real world.
@@danielschaben We used this method to find the strength of tubes. The tubes were made of aluminium alloy. The tubes were for fuel pipes in aircraft, irrigation pipes, scaffold poles and a 1000 and one other uses. They were made in various alloys depending on their application, so they were of various strengths depending on what they were to be used for. They were made to British Standards and Aircraft specifications, requiring a minimum strength in tons per sq. inch. So you needed to know the area of the cross section of the tube. The tube was tested to breaking point in a Tensile Testing machine. The breaking point in tons was then calculated per sq. inch. All these calculations were done on a slide rule, children wouldn't know anything about this nowadays. No calculators then. Hope you find this interesting.
And if all sides are equally
Thanks for letting me learn this complicated skill when I'm Grade 4
Your welcome
Grade 4!? I’m learning this in grade 7 😂
@@Vampyrs__ I know right 😭😭😂😂
One more thing, what if the two radiuses are disconnected???
Sorry I did not get this message in time. For some reason I am not getting notifications for all of my videos. Sorry I couldn't help you.
awh ;(
Are we meant to mutiply the answer by 3.14 or leave the answer in 2700^?
You can do either. Most of the time in a math class we leave answers in terms of pi
@@danielschaben oh tnx
@black berry what do you mean? Are you talking Interest? Stuff like That?
Do I have to multiply with Pi?
You can leave the answer in terms of pi in a math class, but if your building something real, you would have to multiply by some approximation of pi
don't you have to do 2700 x PI?
many times the answer is left in terms of pi. This gives the exact answer. multiplying it by 3.14 will only give and approximation. So it really depends on the precision needed. maybe 3.1415 is needed or 22/7.
Thanks so much
No problem
Question and this is a problem with your method. What abut with decimals? I have a question to work our the shaded area, the larger circle has a radius of 4.1 whereas the smaller one has a radius of 1.7. Now this is where I am having a problem with your method, the answer has to be given to 3 significant figures. Now I can work out the areas of both circles thanks to Pi, however the resulting answer as a whole does not give me the availability to give the answer to 3 significant figures.
(4.1)^2(pi)-(1.7)^2(pi) = 13.92(pi) so now just multiply13.92*3.1415 = 43.72968. So three sig figs would be 43.7. My method works nice so we can eliminate some of the rounding errors that occur by waiting to use the approximated pi until the end.
And thanks for the comment! I love questions
cool
I'm studying right now and doing a question where the radius of the circles arent given. Only the tangent of the smaller circle where it hits the bigger circle. The distance between those 2 points are given. I have no idea how to do it. Any idea?!?!?
I would love to see the picture
Imagining it. You can probably connect a radius to the tangent to make a right triangle and use Pythagorean theorem in there somewhere is my guess
@@danielschaben I just posted a 10 second video of the picture of it, if you want to look at it. I'm not sure if u can use pythagoras but I dont think so. It's in the chapter of trigonometry and the answer is in the back of the book if u want it but it doesnt tell how it's done. Thank you so much!
Thanx
What if only the radius of the small circle is given? How do you find the radius of the big circle?
depends on what the relation between the two circles are
how to derive the formulas of concentric circle??? That's my report on Friday...
+Daniel Schaben thanks, but I'm looking for the derivation of the formulas π(R-r) , π(D-d)/4 and π L²/4..
Thx
Hi thank you for your helpful video, how could i find the number of hectares in a circle with a diameter of 700 miles?
pi*350^2
and then 1 square miles is about 259 hectares so multiply the number. so then multiply the 384845.10*259 = 99674880.9
That's great thank you, I have wrote a story where there is a 700 mile circler area that I guesstimate at 100,000,000 hectares, it is one short story of 6 that I have wrote, and it was just making sure that was right before publishing my book of short stories.
@@JFWILSON220 love it!!!!
...so what's the area of the circle is the bigger portion measures r= 30 inches and the smaller part measures r= 40 inches?
Well.... the bigger circle has to have a radius of 40 and the smaller circle would have to have a radius of 30. Look at your problem again. Are they giving you a diameter or d = 40 on the smaller circle. If that is the case then r = 30 for the larger circle and r = 20 on the smaller circle.
_lh3.googleusercontent.com/ZhixPqPj0xj6zGONWs8vbQuhi87oBUhIgLpa2qt85TTzEObZk9koaNHFgmWXmqFrREGBMHIJSw_
cant open the link
_lh3.googleusercontent.com/-Q8SbF_JdEeaoolx-pvwn9-MjOAIBBUlT8ebqCcW7zHLcxx7CHP4-SJeMOaL4jZy1_xx16UY0g_
Franchezkaichi Sendou what country are you from? Could you just paste the wording of the problem. I can't get either link to work and probably shouldn't click on links I'm not sure about.
OMG thank you so much 7th grade ehriched is hard :D. Math isnt my strong area.
YOU'RE welcome. So glad I could help. If you ever need a video done let me know. If I have time I love making them for good questions
But what about the angle?
In this case we are using the entire circle, so there is no need to worry about the central angle formed by the two radii. If area of sector is what you need, the do a search for area of sector. The area between two things is BIG AREA - SMALL AREA no matter what shape you deal with.
I love you
I know I liked this and loved it, but I think I love you too. LOL. Have a great one. Keep doing math.
can someone show me the the proper procedure
I don’t understand how you got the answer I thought to work out an area of a circle is radius^ times pie (3.14) and to get the area of the shaded area You minus the area for the smaller circle 60^=3600x3.14=11,304 - 30^=900x3.14=2826 So it’s 11,304 - 2826= 8478 so how did you get the other answer
I just left the answer in terms of pi. 2700*3.14 is the same as what you have.
@@danielschaben Ok thank you for the reply
Thx for this im so bad at this now i know how to answer this kind of Problem
But the problem asked to my assignment is the
Radius is 7cm and then added more 7cm and the radius is now 14cm
14*14*pi - 7*7*pi
Can you help me please I need the answer a question in general apilites,, we have two circles a one inside the other. The area of the big circle is 36 pi,, what it provided is that there is a short line which measure 2,, it's out from the border of small circle into the bigger one,, where can I send you the photo of it
I think I know it from your description. You know the radius of the big circle is 6. Because the pi*r^2=36 pi. This means that your inner circle has a radius of 4. The area of this circle is 16pi. So the area of the shaded region between them would be 20pi. Because you would subtract them.
@@danielschaben yes yes this is answer,, but the teacher asked if there commen thing between them like a relationship or law that whenever I see a same question can answer it faster (we are supposed to answer every question in 1 min)
@@danielschaben I do appreciate your answer you don't know how it means to me
For example if once I see the question I know that the big circle area is twice of the small one (I know it's incorrect but Iam giving you an example to understand what I mean with a "faster relationship between them" and that I can do it with all questions with same provided informations
@@user-ok4fv9jq5h square root the area of the bigger without pi sqrt(36)=6, subtract that number from your distance between circles 6-2 =4, square the 4 which is 16. Finally place back the pi and subtract. 36pi -16pi = 20pi
Hey guys its me Gio from paul w bell if u see this ily
Nice math
thanks
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I have depression!
SAAMMEE
I dont understand why your putting Pi after u get ur answer its making me confused
Great question. I'm just leaving pi out of the final calculation. If you take the number multiplied by 3.14 or some other approximation of pi, then you will have an approximate answer. Leaving pi there is just a way to show the exact answer. Now if your question is why is pi in the formula to begin with... well then... that truly is a great question.
@@danielschaben ok now I get it thanks
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people who still need help and found this video
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