the trick is you arent measuring travel on circle B's circumference but rather travel around circle C which is the circle formed when tracing the path of circle A's centre. hence the diameter is A+B or 1+3=4 and 1 goes into 4 four times. got that at around 5:30
@Raphael-hk2um Says:
But what about the other way around, like how many revolution does the circle B take to rotate around A
@philosophyforum4668 Says:
The quarters rolled the same both times – twice. The first time, you counted it right. The second time, you just sort of ignored what happened.
@rkm2999 Says:
why 4? I don't understand, I thought a revolution is equal to 360° or 4x90° to complete, but the coin A only rotated half and he counted it already as one revolution?
or maybe the question is wrong, maybe it's asking how many half rotation the circle A
takes to revolve around circle B?
or maybe i just don't really understand, my answer still 3 😂
edit: oh they fixed it already, i'm jumping to conclusions then
@hoof8670 Says:
I just visualised it came to 4 and was suprised it wasnt an answer :D
@saradoingstuff6650 Says:
My physics teacher showed us this in class 😭😭
@LionStraws Says:
somehow i got this right by adding the radius of the big circle plus the small one then finding the circumference of the 4/3 radius circle and dividing it by the 1/3 radius circle. And ofc using circumference = 2pi*r
@reeturajgogoi5478 Says:
Lol I got it correct on my first try
Am I genius
@ReapingTempest Says:
This is also wrong, the reason being they want the reference point to be the point of Circle A touching Circle B. When A goes around B the reference point only touches 3 times. In the explanation you count how many times the letter A is upright, not how many times the reference point makes a full loop.
@alancornejo318 Says:
11:18 Wow....😂
@alancornejo318 Says:
6:00 Crap I don't understand
@gauravgupta200 Says:
Life was easy while my answer was 3. Now I can't take it anymore 😂
@strnbrg59 Says:
Gosh, I hope Doug Jungreis nonetheless came away with a decent SAT score.
@robertkattner1997 Says:
That is why I always buy an extra large pizza, the best value.
@mewrongway Says:
I got that one right! It was that tricky 2+2 that got me!
@perfectlygoodwasteoftime Says:
I picked b. At least I'm in good company.
@loganle-us6oj Says:
i just want to say it said dec 32
@Unit987 Says:
what
@syedmdabid7191 Says:
111 revolutio responsi(3)
@rooftile883 Says:
It is always the one radius devided by the other PLUS one. In addition to turning around the other circle, it's also making one rotation around it's own axis.
@9999Emac Says:
It's interesting that a math problem's ability to be solved was hindered both by poor English writing skills and ambiguous perspective. I think the issue of correctly translating math to English is going to become worse rather than better based on what I've seen of bad translations (math to English) in textbooks and on tests.
@nico2006t Says:
I knew directly is was 4 and would have also contacted the organisation. Does it mean I am Intelligent lol ?
@AbhinavKumar-kh8ct Says:
Got it 4. find out the radius of perimeter the center has to rotate. If smaller is r and bigger is 3r so radius of rotation will be 4r. Then just equate the perimeter....
@LuckySajuSecret Says:
한글 자막 번역이 매끄럽지 못해요 잘 못알아 듣겠어요 너무 딱딱해서
@AlmostOffline Says:
"SAT is slowly becoming a thing of the past" ... that didn't age very well.
@DizGaAlcam Says:
I got it right xD
@cibonthesaint8903 Says:
You’re wrong. The coin rotation paradox is flawed. The 1/4. You rotated around the other only rotated 50% of the length of of its circumference when it reached the 6 o’clock position.
@SamuelVella1995 Says:
I paused the video at the start, pulled out a paper and pen and figured this out. Initially, 3 seemed correct but then I realised that the path the center of circle A would take would be a circle with a radius of Radius B + Radius A. Assumed Radius B = 1, so radius A = 1/3, therefore the radius of the path of travel would be 4/3. Then, figured out the circumference of the path of travel to be 8/3*pi. Then, divided 8/3* pi by the circumference of circle A, which worked out to be (8/3) / (2/3) = 4.
Was not expecting to be right, but happy that worked out.
@arneshpal7702 Says:
this is easy bruh
@pablocopello3592 Says:
If you are familiar with the difference between sidereal and solar day you should see the correct answer (4) immediately (there is 1 more sidereal day than solar days in one year).
Another way to see it: consider the reference frame in which the center of A does not move and circle B rotates counter clockwise 1 time: circle A will rotate 3 times clockwise in that referential, but that referential rotates clockwise 1 time with respect to the original referential, so in the original referential: A rotates 3+1=4 times clockwise (and B rotates -1+1=0 times).
@ITHrealXD Says:
so basically people who have birthdays on feb 29 arent the most unlucky
people with birthdays on feb 30 (367 days) are most unlucky
@ITHrealXD Says:
i picked 4 first then 6, i havent watched the rest of the video
tell me if one of my answers are right
@Listenandchillzz Says:
So what do you want to expect for a question that does not include thr correct answer in the choices? they will got it all right?
@ozhotz5417 Says:
A much simpler way to explain it: Moving the coin around a 0 length point still takes one rotation!!! Try it rotating the coin around a pin and you get 1 rotation.
@ozhotz5417 Says:
Stick a pin in the table and rotate the coin around it. You will see that the coin rotates 1 time. Rotating the coin around 0 distance still takes a rotation, then you add the length of the coin if you rotate it around a coin, adding to make the 2 rotations.
@DutchDread Says:
I had it right. One hint was that everyone got it wrong, which most definitely wouldn't have happened if ANY of the answers had been correct.
@user-jd3gf5xw1x Says:
at the end, I kinda hope that you would've asked him to show 1 of his questions and quiz us
@abenzer3033 Says:
Love this channel
@MajaEnen Says:
It's just a matter of definition of "rotation". If we define rotation as a 360 degrees turn made by the point tangential to the large circle (which is the proper meaning of "rotation") then answer "3" is correct, as it was given in the SAT answers.
@b10benignojosem.nevallo54 Says:
So 4 was the answer?
@Mike_Rottchburns Says:
My guess: 3, because it’s pi times diameter
@carlfrye1566 Says:
This makes me more appreciate my career did not require intense math knowledge.
I remember my 1st Algebra class and thinking..."why in the world do I have to know this"?
LOL.
@jeremysteinmeier1701 Says:
The more intuitive solution is when the head is facing up again (1 rotation), the edge of the coin hasn't actuality traveled the full distance of the circumference. The circle path adds a rotation to the required 3.
@crystalized7206 Says:
It says revelution not rotation so technically the answer is one
@JackDespero Says:
I needed to watch the video twice for the intuition to settle, but I think I finally got it. It is one of those paradoxes that is hard to understand even when you know the answer. Then it does click and it makes total sense. It is so obvious that you are confused as to why you were wrong the first time. The world is fascinating.
@JackDespero Says:
I find it so funny that the SAT is a multichoice test.
The equivalent to the SAT in my country is just questions, so there is no way to try to guess them.
In fact, I have never done a multichoice exam in my life. It is such a weird concept.
This is a classic example of why multichoice tests are such a weird choice (haha): Even if you are not sure whether it is 3 or 4, since 3 is the only one of the two presents, then you just go with the flow. With a normal test, now that would have been bad.
@whatintarnation4969 Says:
when you’re showing 4 as the answer, the smaller circle is not doing a full rotation. the starting point is different for each point at 1,2,3 and 4. when showing 3 as the answer, the smaller circle itself is making a full rotation
@shyamalganguly3598 Says:
I think there's a easier solution to the problem and it's nearly there when the bigger circle cut into a straight line and now the smaller circle (1/3rd the in radius) is cut and laid on the bigger line and you turn the smaller one 180° for half the revolution of the smaller circle; thus to complete one rev of the smaller it has to make another 180° turn on the straight path of the bigger circle and for next 180° turn the half of the complete rev takes the smaller line (the perimeter) to end of the bigger circle where it has been severed to make it a straight path but to get to the same position for the smaller circle it mus make another 180° turn further with one end of the smaller tied at the end of the bigger line made out of the bigger circle! Therefore, unless the smaller circle makes two full revs along the perimeter of the bigger (3 times the radius of the smaller circle) it won't be able to reach the same position where it started and one less of the total two revs would make it touch the point just below half the rev (180°) from where it has been!
@constancevigilance8696 Says:
I am comforted that you made the same mistake than I.😂
@mzibrahim1 Says:
Cleared this misconception of rotation coin paradox.
THANKS Sir
Love from india
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