Problem for the non-math phobic

[Lsbcal]

I got this old SAT test problem wrong for the same reason discussed by Derek Muller in this Veritasium youtube video. There is interesting history associated with this SAT problem which is discussed. This isn't just about the answer but goes on to talk about some associated applications.

BTW, I don't like tests nowadays and could have bad dreams just thinking about having to go through the hoops we had to in our youth.

 

[Exchme]

I saw this pop up on my U-Tube feed a couple weeks ago, but didn't click on it as the answer seemed obvious...except it wasn't.

 

[PaunchyPirate]

Ha, this also popped up on my YouTube feed this week and I had watched it. It was very interesting to me.

 

[braumeister]

Ha, this also popped up on my YouTube feed this week and I had watched it. It was very interesting to me.

Same here. I found it fascinating.

 

[Gumby]

I made the mistake of assuming that one of the given answers must be correct, so I picked the one that everyone else picked. I should have thought more about it.

 

[Lsbcal]

I made the mistake of assuming that one of the given answers must be correct, so I picked the one that everyone else picked. I should have thought more about it.

But would you have come up with the right answer if you just had to do the problem not looking at the multiple choices? I would have still missed it.

 

[Gumby]

But would you have come up with the right answer if you just had to do the problem not looking at the multiple choices? I would have still missed it.

Maybe, maybe not. My immediate thought was the common one, but like a good test taker, I also evaluated the alternatives and determined that they made no sense, so I stuck with my first thought. At the same time, however, I had a feeling that there was something wrong with that number, but I didn't go further. Although, even with further thought, I still may not have come up with the correct answer.

 

[Ronstar]

One would think the answer would be 3 based on a full revolution of the small circle being its circumference as measured along the big circle. But that isn’t it. Correct answer isn’t listed.

 

[jldavid47]

The answer has to be 2. (I only looked at the problem not the entire video). If rA = 0.5 * rB then dA = 0.5 *dB. Since circumference is pi * d, then the circumference of B is twice the circumference of A. Therefore it takes two revolutions of circle A to get back to the original position.

Maybe this is one of the few SAT math questions I "missed" when I took it because I was forced to guess what they thought it was.

 

[Lsbcal]

The answer has to be 2. (I only looked at the problem not the entire video). If rA = 0.5 * rB then dA = 0.5 *dB. Since circumference is pi * d, then the circumference of B is twice the circumference of A. Therefore it takes two revolutions of circle A to get back to the original position.

Maybe this is one of the few SAT math questions I "missed" when I took it because I was forced to guess what they thought it was.

You need to go further into the video for your own good.

 

[DrRoy]

Well, I'll be darned.

 

[Badger]

I was never a good math student so I would have probably passed this up and only returned to it after I finished all the questions in which I was sure. However, I did find a question in the Biology GRE that was either ambiguous or didn't have a correct answer. At that time there were 3 possible tests you could get and I got the one that I had the least experience and had to guess at some answers. I must have been lucky that day.
I'm glad that is all behind me now.

Cheers!

 

[braumeister]

When I looked at this, I realized it was easy to calculate so I got the answer right away. It was wrong, of course, but quick and easy. Made the same mistake the test designers made, just like most others. Really enjoyed the video explanation though.

 

[donheff]

Now that was a fascinating video. It even cleared up the concept of sidereal time which has been confusing me as I do my deep space astrophotography. Thankfully, software keeps track of this stuff, so we don't have to.

 

[Chuckanut]

Writing good tests is hard. The human brain seems designed to find and display every fault imaginable no matter how thoroughly an item has been tested to assure it works properly. I bet the engineers in our group can tell us stories!



In my Ed. Psychology class our teacher told us about a test given to lower income students in a NY city elementary school. One question showed a picture of a pine tree, a flower, a head of cabbage and a cactus. The questions asked "Which of these plants needs the least amount of water? The obvious answer is the cactus. A young boy of about age 8 picked the cabbage. When asked about why he chose the cabbage he replied, "Look at the picture. It's been picked. So it doesn't need any more water."

 

[Trooper]

Pretty interesting stuff!

In my Ed. Psychology class our teacher told us about a test given to lower income students in a NY city elementary school. One question showed a picture of a pine tree, a flower, a head of cabbage and a cactus. The questions asked "Which of these plants needs the least amount of water? The obvious answer is the cactus. A young boy of about age 8 picked the cabbage. When asked about why he chose the cabbage he replied, "Look at the picture. It's been picked. So it doesn't need any more water."

Love it!

 

[Koolau]

This all reminds me of a little math "quiz" that was going around when I was in 8th grade. It wasn't at all complicated. You start with a 4 digit number. Fold the paper down to reveal that you must add a 4 digit number. Fold it down again and then do three or 4 more simple additions or subtractions (as I recall) All operations required the paper to be folded down to reveal the required math operation. Then one final addition gets you to the result. But NOBODY I ever watched take the quiz (including our 8th grade math teacher) ever got the right answer. It was all in the final addition. The person taking the quiz always assumed a number and that number was wrong. I wish I could recall this clever fooler.

IIRC, everyone would come up with, say, 8000 when the actual result was 7100 or something like that. It was amazing to watch. I think the previous math operations "forced" the person to assume the next result.

As I said, I never saw it fail to humiliate the quiz taker (including me.) YMMV