Calculate the Radius of the semicircle | Radii of Green circles are 2 and 3 | Fun Geometry Olympiad

Тәжірибелік нұсқаулар және стиль

Learn how to find the radius of the semicircle. Radii of Green circles are 2 and 3. Important Geometry and algebra skills are also explained: Pythagorean Theorem; Quadratic Formula; Circle Theorem. Step-by-step tutorial by PreMath.com
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Step-by-step tutorial by PreMath.com
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Calculate the Radius of the semicircle | Radii of Green circles are 2 and 3 | Fun Geometry Olympiad
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Пікірлер: 85

  • @predator1702
    @predator1702 Жыл бұрын

    Beautiful question and more beautiful explanation 👍. Thank you teacher 🌹🙏.

  • @PreMath

    @PreMath

    Жыл бұрын

    You are very welcome! Thanks for your continued love and support! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @ghhdcdvv5069
    @ghhdcdvv506911 ай бұрын

    تمرين جميل جيد. رسم واضح مرتب. شرح واضح مرتب. شكرا جزيلا لكم والله يحفظكم ويحميكم ويرعاكم جميعا . تحياتنا لكم من غزة فلسطين

  • @theoyanto
    @theoyanto Жыл бұрын

    This was difficult, I never could have done this without the video.. I nearly always find it difficult to get started. Ah well, onward and downward 🤓 But thoroughly enjoyed your solution, thanks again 👍🏻

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks for your feedback! Cheers! You are amazing, Ian. Keep smiling👍 Love and prayers from the USA! 😀

  • @ghhdcdvv5069
    @ghhdcdvv5069 Жыл бұрын

    تمرين جميل جيد .رسم واصح مرتب. شرح واصح مرتب .شكرا جزيلا لكم والله يحفظكم ويحميكم ويرعاكم جميعا . تحياتنا لكم من غزة غلسطين

  • @PreMath

    @PreMath

    Жыл бұрын

    شكرًا عزيزي

  • @HappyFamilyOnline
    @HappyFamilyOnline Жыл бұрын

    Great 👍 Thanks for sharing😊

  • @claudeabraham2347
    @claudeabraham2347 Жыл бұрын

    Very good!

  • @dannymeslier6658
    @dannymeslier6658 Жыл бұрын

    Brilliant! Loved it, thanks

  • @PreMath

    @PreMath

    Жыл бұрын

    Glad you think so! Thanks for your feedback! Cheers! You are awesome, Danny. Keep smiling👍 Love and prayers from the USA! 😀

  • @VictorLonmo
    @VictorLonmo Жыл бұрын

    I was not able to get this on my own. I like a good challenge. Great video PreMath!

  • @odayazeez777
    @odayazeez7778 ай бұрын

    well very useful

  • @luigipirandello5919
    @luigipirandello5919 Жыл бұрын

    Beautiful question. Thank you Sir.

  • @PreMath

    @PreMath

    Жыл бұрын

    Glad you think so! Thanks for your continued love and support! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @fauxcube
    @fauxcube11 ай бұрын

    What a fantastic solution, you have taught me so much from this. I give all my thanks to you.

  • @PreMath

    @PreMath

    11 ай бұрын

    You are most welcome😀

  • @alster724
    @alster724 Жыл бұрын

    Another technique in solving 96r²-500r-625= 0 Is by using the _Edge Test_ factoring method 24 25 4 -25 Then by cross multiplying and adding, we get the value of b (24)(-25)+(4)(25) -600+100 -500 So our factors are (24r+25)(4r-25) r= -25/24, 25/4 Since this is a geometric figure, we take the positive value, we have 6.25 units or 25/4

  • @PreMath

    @PreMath

    Жыл бұрын

    Excellent! Thanks for your feedback! Cheers! You are awesome, Kevin. Keep it up 👍 Love and prayers from the USA! 😀

  • @ghhdcdvv5069

    @ghhdcdvv5069

    11 ай бұрын

    شكرا جزيلا لكم والله يحفظكم ويحميكم جميعا. تحياتنا لكم من غزة فلسطين ​@@PreMath

  • @PreMath

    @PreMath

    11 ай бұрын

    @@ghhdcdvv5069 Thanks dear

  • @KAvi_YA666
    @KAvi_YA666 Жыл бұрын

    Thanks for video.Good luck sir!!!!!!!!

  • @PreMath

    @PreMath

    Жыл бұрын

    You are very welcome! Thanks for your continued love and support! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @bertblankenstein3738
    @bertblankenstein373810 ай бұрын

    Nice. I did not see an obviously solution that could be guessed at, or found by inspection. At always, the building blocks like the quadratic and Pythagoras formulas were there, and the solution lies in putting things together the right way which makes it interesting.

  • @bigm383
    @bigm383 Жыл бұрын

    Thanks Professor, another gnarly little problem!🥂❤

  • @PreMath

    @PreMath

    Жыл бұрын

    You are very welcome! Thanks for your continued love and support! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @bigm383

    @bigm383

    Жыл бұрын

    @@PreMath 🍺😃👌

  • @alexandermorozov2248
    @alexandermorozov2248 Жыл бұрын

    Very nice!

  • @PreMath

    @PreMath

    Жыл бұрын

    Glad you think so! You are awesome, Alexander. Keep smiling👍

  • @murdock5537
    @murdock5537 Жыл бұрын

    Many thanks, Sir, this is a real challenge - and a masterpiece solving it. btw: sin⁡(φ) = 2/(r - 2) = 8/17 → sin⁡(δ) = 3/(r - 3) = 12/13 → φ + δ > 90°

  • @wackojacko3962
    @wackojacko3962 Жыл бұрын

    I absolutely love "Famous Identities" !🙂

  • @PreMath

    @PreMath

    Жыл бұрын

    Glad to hear that! Thanks for your feedback! Cheers! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @alinayfeh4961
    @alinayfeh4961 Жыл бұрын

    we draw Auxiliary lines ON , OT for center and point of contact According Phythagorean thereom Radius rof semicircle r (r-2)²=4+x² x=√(r²-6) (5-x)²+2²=(r-2)² 25-10x+x²+4=r²-4r+4 r=6.25

  • @PreMath

    @PreMath

    Жыл бұрын

    Excellent! Thanks for sharing! Cheers! You are awesome. Keep it up 👍 Love and prayers from the USA! 😀

  • @NLGeebee
    @NLGeebee Жыл бұрын

    Made a sketch in CAD and eyeballed the semi circle. Measured it and is was about 6,3 so it must be 2pi ;)

  • @voltalimwabbit5492
    @voltalimwabbit5492 Жыл бұрын

    Sir can we possibly work out the length of the vertical line M?

  • @PreMath

    @PreMath

    Жыл бұрын

    Good question! Never thought about that...

  • @ybodoN

    @ybodoN

    Жыл бұрын

    When the green circles are in the ratio 3:2, the vertical line is equal to the diameter of the larger of the two circles 😉

  • @timeonly1401

    @timeonly1401

    10 ай бұрын

    I poked around a found the length of the vertical line segment MC (If we call the point C where that vertical intersects the semicircle): From the video, we have r=25/4, and that x=√(r²-6r) = √{(25/4)[(25/4)-6]} = √(25/16) = 5/4. In right triangle AOP, the long leg AO = 5 - x = 5 - (5/4) = 15/4. Since AM = 2, and AO = 15/4, we have MO = AO - AM = 15/4 - 2 = 7/4. Draw radius OC. Then the 3 segments MO, MC & OC form a right triangle. By Pythag's Thm: MC² = OC² - MO² = r² - MO² = (25/4)² - (7/4)² = 576/16, and MC = √(576/16) = 24/4 = 6. Done!! [I'm STUNNED that that vertical turned out to be a "nice number" 6. 😅 ]

  • @zdrastvutye
    @zdrastvutye Жыл бұрын

    it took longer for me than expected because once the root must be substracted and once it must be added, which confused me: 10 r1=2:r2=3:sw=.01:ru=sw:ym1=r1:ym2=r2:ng=r1^2+r2^2:goto 60 20 dis1=(ru-r1)^2-ym1^2:dis2=(ru-r2)^2-ym2^2 30 if dis1

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks for sharing! Cheers! You are awesome. Keep it up 👍 Love and prayers from the USA! 😀

  • @zdrastvutye

    @zdrastvutye

    Жыл бұрын

    @@PreMath thanks for your attention, there was a problem with the result inside the sqr( ). now i have worked this out and have edited and updated the comment

  • @neillawrence4198
    @neillawrence4198 Жыл бұрын

    Finally, a problem that someone didn't claim to solve in 35 seconds in their head.

  • @vara1499
    @vara1499 Жыл бұрын

    👏

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks dear for your continued love and support! You are awesome. Keep smiling👍 Love and prayers from the USA! 😀

  • @kennethstevenson976
    @kennethstevenson976 Жыл бұрын

    Tough problem involving two variables and superior insight to get the problem set up and produce the final answer. Again you gave each step required to produce the answer. I could not do this problem!

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks for your feedback! Cheers! You are awesome, Kenneth. Keep smiling👍 Love and prayers from the USA! 😀

  • @alexandermorozov2248
    @alexandermorozov2248 Жыл бұрын

    Кстати, 2-е решение (когда радиус отрицательный) тоже имеет место быть, оно вполне реальное, и его можно даже построить на рисунке. Задание: подумайте, как это изобразить 😜 === By the way, the 2nd solution (when the radius is negative) also takes place, it is quite real, and it can even be built in the figure. Task: think about how to portray it 😜

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks for your feedback! Cheers! You are awesome. Keep it up 👍 Love and prayers from the USA! 😀

  • @photonomist6345

    @photonomist6345

    11 ай бұрын

    I was wondering and thinking it must mean something, but I am not clever enough to visualise it!

  • @alexandermorozov2248

    @alexandermorozov2248

    11 ай бұрын

    @@photonomist6345 :) I can build a drawing with visualization especially for you.

  • @alexandermorozov2248

    @alexandermorozov2248

    11 ай бұрын

    @@photonomist6345 A negative radius can be represented as a radius laid in the opposite direction (hint).

  • @photonomist6345

    @photonomist6345

    11 ай бұрын

    @@alexandermorozov2248 Thank you! I have it!

  • @tehribo
    @tehribo Жыл бұрын

    How do we know that ON and OT pass through P and Q

  • @rchandos

    @rchandos

    Жыл бұрын

    We don't know that in advance,. He assumes that they do, contingent on locating the center of the semicircle such that ON equals OT.

  • @PreMath

    @PreMath

    Жыл бұрын

    Dear TB, I believe I covered this topic in some of videos. Very simple explanation. I'll cover again pretty soon. No worries. Keep watching😀

  • @gelbkehlchen
    @gelbkehlchen11 ай бұрын

    Solution: R = radius of semicircle. From the center of the semicircle to the centers of the two small circles it is R-2 and R-3. These are the hypotenuses of two right-angled triangles whose centers are 2+3 = 5 apart. This gives the equation: √[(R-2)²-2²]+√[(R-3)²-3²] = 5 ⟹ √[R²-4R+4-4]+√[(R²-6R+9-9] = 5 ⟹ √[R²-4R]+√[R²-6R] = 5 |-√[R²-6R] ⟹ √[R²-4R] = 5-√[R²-6R] |()² ⟹ R²-4R = 25-10*√[R²-6R]+R²-6R |-R²+4R+10*√[R²-6R] ⟹ 10*√[R²-6R] = 25-2R |/10 ⟹ √[R²-6R] = 2,5-0,2R |()² ⟹ R²-6R = 6,25-R+0,04R² |-0,04R²+R-6,25 ⟹ 0,96R²-5R-6,25 = 0 |/0,96 ⟹ R²-125/24*R-625/96 = 0 |p-q-formula ⟹ R1/2 = 125/48±√[(125/48)²+625/96] = 125/48±√[15625/2304+15000/2304] = 125/48±√[30625/2304] = 125/48±175/48 ⟹ R1 = 125/48+175/48 = 300/48 = 6,25 and R2 = 125/48-175/48 = -50/48 = -25/24 [invalid in geometry]

  • @alfonsorodriguez2739
    @alfonsorodriguez2739 Жыл бұрын

    I would like to get in contact with you premath. How can I do so?

  • @PreMath

    @PreMath

    Жыл бұрын

    You may email us: premathchannel@gmail.com Thanks for asking. Cheers

  • @Songwriter376
    @Songwriter37611 ай бұрын

    Ok, I knew that. Yep. So, what's for dinner?

  • @4iriska
    @4iriska Жыл бұрын

    Why are we sure that OT and ON go through the centers of green circles?

  • @rchandos

    @rchandos

    Жыл бұрын

    They have to so that both the semicircle and the smaller circles are tangent at T and N. His assumption turns out to be justified because he manages to locate the center of the semicircle such that OT=ON.

  • @PreMath

    @PreMath

    Жыл бұрын

    Hello dear, I believe I covered this topic in some of videos. Very simple explanation. I'll cover again pretty soon. No worries. Keep watching😀

  • @4iriska

    @4iriska

    Жыл бұрын

    @@rchandos Thank you

  • @misterenter-iz7rz
    @misterenter-iz7rz Жыл бұрын

    Rather difficult, this puzzle, 🤔 two circles do not touch each other, but the common vertical tangent, do horizontal distance between P and Q is 2+3=5, let r be radius of the semicircle, so square root((r-2)^2-4)+square root((r-3)^2-9)=5, we can find r by solving this equation, a little bit troublesome.🤨

  • @PreMath

    @PreMath

    Жыл бұрын

    Thanks for your feedback! Cheers! You are awesome. Keep it up 👍 Love and prayers from the USA! 😀

  • @peterkrauliz5400
    @peterkrauliz5400 Жыл бұрын

    Where is the proof that these respective points are collinear? It looks obvious, but how can one be sure!

  • @vaibhavgupta5359
    @vaibhavgupta5359 Жыл бұрын

    Sir what is your age

  • @PreMath

    @PreMath

    Жыл бұрын

    Dear Vaibhav, I'd talk about myself pretty soon. I can understand your curiosity. Thanks for your continued love and support! You are awesome. Keep smiling👍

  • @wackojacko3962

    @wackojacko3962

    Жыл бұрын

    I absolutely love "Famous Identities"!🙂

  • @SohailKhan-xx8wi

    @SohailKhan-xx8wi

    Жыл бұрын

    35years old.

  • @vaibhavgupta5359

    @vaibhavgupta5359

    Жыл бұрын

    @@PreMath sir you have a sharp brain I want to know how do u relate all the concepts of maths so easily

  • @maturaczynicuda

    @maturaczynicuda

    Жыл бұрын

    @@vaibhavgupta5359 true, the possibility of learning from such a great teacher is a great privilege

  • @mohamadtaufik5770
    @mohamadtaufik5770 Жыл бұрын

    (R^2-6R)^0.5+(R^2-4R)^0.5=2V6 --> R=6.223

  • @ybodoN

    @ybodoN

    Жыл бұрын

    If the two circles were tangent, this would be the correct answer...

  • @mohamadtaufik5770

    @mohamadtaufik5770

    Жыл бұрын

    I thought there were tangent, thanks for the correction

  • @user-ye6re7wq6c
    @user-ye6re7wq6c8 ай бұрын

    Difficult

  • @johnplong3644
    @johnplong3644 Жыл бұрын

    Ok I need help with this one

  • @wajiraabayasinghe7718
    @wajiraabayasinghe771810 ай бұрын

    First go to a school and lean how to pronounce English Language. Your Math skills are good but pronunciation is to be improved

  • @amitabhshrivastava3121
    @amitabhshrivastava312110 ай бұрын

    You can still solve even if the green circles were tangential

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