Most US College Students Cannot How Many Holes Does A Straw 2 months ago   07:14

MindYourDecisions
To complete a job, it takes: Alice and Bob 2 hours, Alice and Charlie 3 hours, and Bob and Charlie 4 hours. How long will the job take if all 3 work together? Many, many US college students set up the equations incorrectly and get the wrong answer. Can you solve it? Watch the video to understand the correct method and answer.

*Small correction: At 2:19 I incorrectly said "four fifths" and meant to say "four point five."

My blog post for this video
https://wp.me/p6aMk-5h1

Sources
Toom, Andrei. "A Russian teacher in America." Journal of Mathematical Behavior 12.2 (1993): 117-139. See the "Tom, Dick, and Harry working together problem" (page 134 in text). https://faculty.utrgv.edu/eleftherios.gkioulekas/OGS/Misc/ARUSSIAN.PDF

Jerome Dancis, Associate Professor Emeritus, University of Maryland, Algebraic word problems. www.math.umd.edu/~jnd/Algebraic_word_problems.pdf

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Comments 4335 Comments

CQUNC
4.5 is now pronounced "four fifths" (2:19).
Frank Herrera
I worked at 800 W. Montana. Had a college kid come in asking for a business located at eight hundred and one Montana. I told him 801 Montana was the big church across the street. "No,no! Its a business and I have an interview in 5 minutes!" I looked at his paper work. He was looking for 8001 Montana. "Forget it kid, you're not getting the job. First of all, you won't make it on time. Secondly, if you tell them why your late ......." true story.
Dirk-Jan Ten Kate
P
martybadboy
Charlie = union slug
Ed Andrews
The problem requires someone to look and see that if two people can do it in two hours, then additional people can do it in under two hours. However, it assumes that the job can be organized so everyone is occupied. That is an assumption that is unjustified. For example, the type of work may not allow it to be divided in small increments.
E Loesch
Simple, 4.5 hours.
Tana Murphy
Alice = 1 hour, Charlie = 1 1/2 hours Bob = 2 hours. Do we add or add and divide to find the average?
Tana Murphy
I'm lost. This is why I couldnt do algebra.
Subash Babu
I'm from SG and I was taught how to do this question when I was 11
PushandillPushback
The answer is 1 hour
Jorge Castillo
Well I got it right by using more or less the same ecuations but I got the percentage of how much of the work is done by each person in one hour and here is my results.
Alice gets 29% of the job done in one hour
Bob gets 21% of the job done in 1 hour
And Charly gets only 4% of the job in 1 hour.
David Marlow
2 hours... Alice and Bob kick ass. Charlie is a loafer and to be FIRED! YOU'RE FIRED CHARLIE! YOU POS! LOL
EpicDoggiez
Charlie only contributes 9 minutes. WAKE UP CHARLIE! STOP SLACKING!
History is Fake
The question is nonsense, Alice could never complete a job faster than the men.
Mahulan c
Logic Think for this ... alice is hard worker, And bob itd a true man and alice finish half work in 2h + bob this same, nów if charie is lazy than he mąkę 50% of work in 2 h. Nów if bob work with charie and see lazy guy than he too work słow (logic). If we ADd all together alice and bob need mąkę together 66% of work than should be around 1h 20min and +luzy guy who feed mąkę 33%of work (hmmm i should dont give +~30min becous in Real live they work all togheter in this same time) Thats why i give 15 min(luzy guy... only if he will work in my team we go Help him to finish more fast. The answer ~~1h30 min !! (If help charie give me only 9 min more fast finish work than i kick him out after 30min in work (becouse he will do maby less than 5 %) thats true live. Śry bąd english (need more practis)
Updesh Singh
3 hours
densch123
general formula:
1/(1/a+1/b+1/c) for a,b,c working together.
Lulu Tyson
🤯......... subscribed!!!
IamTheSnowman4
The truth is that when working with a woman a man can work twice as hard (doesn't mean time efficiency but may result in it) so that he can impress her. This effect is similiar to people working out in a gym, the crowd effect of thinking people (of the desired gender) are watching urges the body to ignore any problems and focus on the task. While Charlie is clearly slower than Bob it is however possible that Charlie may have had a better quality result rather than completion with a focus on time. If we insert one more woman into this question and pair her with Alice would they work faster to impress eachother or would they spend all their time gossiping about drama. Would it be faster if the two women knew eachother or if it was their first time working together?

Using math to solve an estimation/psychological problem may not lead to the right answer but it can be used to put work efficiency into perspective.
Justin Credible
I came to 1 45 right off the top of my head. I never went to college.
Add Reply

How Many Holes Does A Straw Most US College Students Cannot 2 months ago   04:21

This question has generated a lot of debate online. BuzzFeed's video has 450,000+ views already. But the question has a mathematical interpretation with a correct answer: in topology, how many holes does a straw have? I explain and animate the answer in the video. It's great to see topology go viral!

My blog post for this video
https://wp.me/p6aMk-5sB

BuzzFeedVideo
https://up-tube.com/upvideo/J0gLEIDiXoZ

Drinking Straws: How Many Holes? Kevin Knudson, professor of mathematics at the University of Florida
https://www.forbes.com/sites/kevinknudson/2018/01/29/drinking-straws-how-many-holes/

2016 Nobel Prize in Physics
https://www.nobelprize.org/nobel_prizes/physics/laureates/2016/

If you like my videos, you can support me at Patreon:
https://www.patreon.com/mindyourdecisions

Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you.

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If you buy from the links below I may receive a commission for sales. This has no effect on the price for you.

My Books
"The Joy of Game Theory" shows how you can use math to out-think your competition. (rated 3.8/5 stars on 31 reviews)
http://amzn.to/1uQvA20

"The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" is a handbook that explains the many ways we are biased about decision-making and offers techniques to make smart decisions. (rated 4.6/5 stars on 3 reviews)
http://amzn.to/1o3FaAg

"Math Puzzles Volume 1" features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.4/5 stars on 13 reviews.
http://amzn.to/1GhUUSH

"Math Puzzles Volume 2" is a sequel book with more great problems. (rated 4.3/5 stars on 4 reviews)
http://amzn.to/1NKbyCs

"Math Puzzles Volume 3" is the third in the series. (rated 3.8/5 stars on 5 reviews)
http://amzn.to/1NKbGlp

"40 Paradoxes in Logic, Probability, and Game Theory" contains thought-provoking and counter-intuitive results. (rated 4.3/5 stars on 12 reviews)
http://amzn.to/1LOCI4U

"The Best Mental Math Tricks" teaches how you can look like a math genius by solving problems in your head (rated 4.7/5 stars on 4 reviews)
http://amzn.to/18maAdo

"Multiply Numbers By Drawing Lines" This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. (rated 5/5 stars on 3 reviews)
http://amzn.to/XRm7M4