Find the Radius 

engineers: yeah, should be around (9+12). Put a box around it.

i was so confused for a while why it wasnt just 9+12, i think i need to go back to basic geometry classes...

You can actually see that r is slightly more than 21, so the final answer is most satisfying.

All this to add ".25" to the radius, i'd say that is 21.4 without thinking

"how exciting" always gets me

Blue jaguar! I like your videos, keep making them 👍

Another way to arrive at x = 13/4: Use the intersecting chord theorem by filling out the rest of the circle and extending the 12 cm segment horizontally until it hits the circle’s left side (that will make the chord 12 + 9 + 21 long). Similarly, extend the 16 cm segment vertically to hit the circle’s bottom (chord length 16 + x + 16 + x). Then you have the relation: (12)(30) = (16) (16+2x), giving x = 13/4.

Great animation, If I had this description and animation in grade 2 i probably would’ve understood it!😊

Never stop making uploading i dont know what i'd do without these videos😞

Man, I struggle with this stuff but I’m going to keep trying until it makes more sense.

hey andy i really appreciate you showing all the steps, i know how to do the rest once u do the first few steps but i wish my teachers would show ALL their work when i was learning this stuff. really helpful for those who aren’t familiar with the techniques

Gotta admit it did confuse me lol but I liked the part with the yellow gecko :)

Blue deer! I ALWAYS read the description box!

Thank you so much for these question, I want to be a scientist and you gave me a good practice of math.

Red sloth! I find these videos really helpful

Cool stuff, I always forget you can draw radii as much as you want 😓 Emerald Spider

Nice one again, keep up the good work

I love how you explain seemingly complex thing in a simple way. Nice video Andy!!

Im in 6th grade and this guy did it in a way i could understand. good job man!

That was pretty slick mate, I enjoyed that.

It was really easy, but glad to solve it Thanks bro

Good problem! My solution was identical, so I wonder if there's a significantly different way to approach this.

It is best to do it with coordinate geometry as follows If the center of the circle is the assumed origin then the equation of the circle would be x^2 + y^2=r^2 Point A which lies on the top end of the 16cm line has coordinates (9,16+k) where k is the clearance of the 16cm line from the ground and the point B on the circle which is the right end of the 12cm line has coordinates (21,k) We have two equations that correlates R and k. Solve and you are done

How exciting! Dont you love pink capybaras?

Put a box *inside* the quarter-circle; put a box *around* the answer. How exciting!

I'm partial to forest green and I love the Manta Ray.

Hey I love your videos! Where do you/dis you go to college?

Great explanation of the full process.

Gotta love problem solving.

Blue Chameleon

I not only like maths but also your vids

turquoise bison man i love this one

Able to do that by myself, feel like still worthy

I would never solve it by myself, but now i know how,thank you !

I watch your videos while I shower so that I always start my day with some math 👍🏽 how exciting

I feel like he made things excessively harder by not just using decibels and continually using fractions. It added so many more steps than if he just simplified his fractions to decimals as he went.

blue capybara

How exciting!

i really like geometry, i can't believe that people can't understand the simpler things like this!

I use these shape video's to help me draw in fusion 360. Thx

Carry a ruler. Measure the lenght of a known line. Measure the lenght of the radius. Use this ratio to get the actual lenght of the radius. Problem solved. Used this shortcut plenty in school and college. Works especially well for MCQs when time is a factor.

Hello, I am from China and am a middle school mathematics teacher. Can you tell me which software is used for the demonstration? I want to use it for my students，万分感谢

Little bit too fast, but very nice. Good job man.

One day I will figure out the puzzle solo 😔

where do you find these questions?

I eyeballs it at 21.smidge so pretty happy with the result.

I used a very similar method, but only one variable.

Blue Aardvark.

This might actually might be regarded

Oh, that was much less convoluted than what I did. I drew the segment bisector on the chord, knowing that it goes through the center of the circle, and used similar triangles. I guess your solution is fine too.

i solved it in basically the same way, but i just used decimals instead of messing around with fractions.

Green octopus!

my favorite colour is honestly beige and my favorite animal is capybara😀

Thanks a very good video

Yes, needing two ways to verify x in simultaneous equations. I got there eventually, but it took me a while to figure out where to make the second equation.

green narwhal!

Turquoise crab

4r² = w² + x² + y² + z² from what is given, you can deduce, that the values needed are 30, 12, 16 and 22,5 Those values squared are 900 / 144 / 256 and 506,25 Sum of which equals 1806,25 that divided by 4 equals 451,5625 Square root of which equals 21.25 and you are done.

color-grey animal-Dog

Problem got its own problem.

Pink penguin

purple, alpaca

This is the process which my teacher want me to do 😂

i really thought this video was a joke until i realized the 12 cm line is not hittin the actual edge of the circle

Purple axolotl

Has to be a Green Orangutan

blue and idk about animal but hey your smart.

Very exiting indeed

Hey! Just wanted to confirm, do you find it easier to use Pythagorean theorem than to just add 16 and 13/4 in the final step? This is a genuine question I am not trying to be sarcastic or anything.

Purple vulture!

green cat ...am i the only one that did this?

"It's a little more than 21. Next..."

How exciting indeed!

Nice geometry problem❤

Purple Maned Wolf

green giraffe

That was awesome

Teal beaver.

Black, Red Panda !

Nice one

Orange Seagull

How exciting

EXCITING. SO EXCITING.

Blue Koala If you have no idea what I'm talking about, you're just streets behind.

white mantis

Estimated 21.23, this is why Id fail math another time around. "Eh close enough" is as accurate as Ive ever needed to be

This is how I did it with video paused, check both triangles, mismatch, go back find my mistake, check again r=21.25 how exciting

I liked the deep RRR xD

Purple panda heheh

pink squirrel baybeeee

Purple Fox

blue seal

me: pfff.. 21 look at video length: hmmm

Blue rhino!

Black Iguana

Blue penguin!

Pink Catfish

a 10th grade problem in which i made same mistake again lol

I just stuck a pencil in my eye...

Why are Pirates called Pirates? They just arrrr... 😇