The Mathemetics Thread

[Lily Adler]

 

[Dr.]

By my reckoning, the answer is 42.5. But the problem seems to contains a typo — since the answer, in the real world, should work out to a whole number of dogs. Alternatively, a more plausible subject should have been used. E.g., fractions of candy bars make sense; whereas, fractions of dogs do not.

These types of puzzles (sneakily) rely on the reader misinterpreting the question. A related one is this old classic:

A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?

Most assume the ball must cost 10¢. Which is incorrect.

 

[Lily Adler]

 

[blueharvest]

 

[Dr.]

Louisiana students Ne’Kiya Jackson and Calcea Johnson wowed their teachers in 2022 when they discovered a new way to prove the 2000-year-old Pythagorean theorem... Now Jackson and Johnson, who started college last year, have notched another achievement: authoring an academic paper detailing their original proof — plus nine more. Their work [was] published Monday in the scientific journal American Mathematical Monthly.

https://www.cnn.com/2024/10/29/science/teens-pythagorean-theorem-study/index.html

 

[Dr.]

Math humor.

 

[:eek:]

Infamous 'sofa problem' that boggled mathematicians for decades may finally have a solution

A math problem delineating the largest-size sofa that can fit around a corner has finally been solved, though it may not help you move.

www.livescience.com

 

[Lily Adler]

 

[Dr.]

Lot’s of math teachers on Youtube — some better than others. And I’d highly recommend “Math Queen.” Many of her videos tackle a particular puzzle and then walk you through the solution via exceptionally good step-by-step instruction. One example (among many on her channel):



(In this case, some familiarity with “systems of equations” is assumed.)

Math Queen is Susanne Scherer. And although her English language math videos are relatively new, she’s been doing the German version for longer. Also… she’s a singer — a member of the band MoonSun — with a fairly impressive voice.

 

[:eek:]

Mathematicians discover a completely new way to find prime numbers

Using a notion called integer partitions, mathematicians have discovered a new way to detect prime numbers while also connecting two areas of math in an unexpected way

www.livescience.com

 

[blueharvest]

 

[InCali]

First time I've seen this thread so sorry about dredging up old stuff.....

Yeah.....in this case there has to be an even # of dogs or an odd number must be the difference in the number of small to large dogs. Basically, both numbers have to be even or odd for it to work out unless someone was really mean to a large and a small dog.

By my reckoning, the answer is 42.5. But the problem seems to contains a typo — since the answer, in the real world, should work out to a whole number of dogs. Alternatively, a more plausible subject should have been used. E.g., fractions of candy bars make sense; whereas, fractions of dogs do not.

These types of puzzles (sneakily) rely on the reader misinterpreting the question. A related one is this old classic:

A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?

Most assume the ball must cost 10¢. Which is incorrect.

Yeah. It's "basically" the same idea as the dog problem only this one works. You just take the difference between the total cost, subtract the cost of the bat, divide by 2 and add it to the the cost of the bat. The other half is the cost of the ball.

Fun thread.......

 

[Dr.]

In less than 60 seconds, deepfake Morgan Freeman and Jake Paul explain the derivative in calculus. (And they do a decent job.)



Same dude also has Taylor Swift and one of the Kardashians explaining integrals.

 

[Dr.]

The 10th month on the 23rd day — between 6:02am and 6:02pm — is “National Mole Day.”

Because… a mole is a (mass) unit of measure containing “Avogadro’s Number” of molecules or atoms. And Avogadro’s Number is 6.02 x 10^23.

 

[Dr.]

How to calculate percent change:

Using the above formula, it’s pretty straightforward.

For example, going from $100 to $300, you’d plug in the following values: 300 (new) – 100 (old) / 100 (old) x 100. Which simplifies to 200/100 x 100. Which, in turn, is 200 — a 200% increase.

But doing the reverse (e.g., $300 to $100) can be slightly tricky for new students. At first glance, it might seem like a 200% decrease. But not so — because the old/original value is now different, has changed from $300 to $100. Thus: 100 (new) – 300 (old) / 300 (old) x 100. Which is -200/300 x 100; which is ‑66.66… Or a ~67% decrease.

Moral of the story: for real-world financial stuff, a percent decrease can never be greater than 100% — because 100% represents a (minimum) zero dollar amount.

Or maybe not… Stable genius and Wharton School of business grad, D. Trump, thinks the price of goods can be reduced by hundreds to thousands of percent. So what do I know?

Trump’s mathematically impossible promise to cut drug prices by ‘1,000%’​

https://www.cnn.com/2025/09/23/politics/fact-check-drug-prices-trump

 

[GunBlade]

black excellence strikes again

 

[Breogan]

 

[InCali]

How to calculate percent change:

Using the above formula, it’s pretty straightforward.

For example, going from $100 to $300, you’d plug in the following values: 300 (new) – 100 (old) / 100 (old) x 100. Which simplifies to 200/100 x 100. Which, in turn, is 200 — a 200% increase.

But doing the reverse (e.g., $300 to $100) can be slightly tricky for new students. At first glance, it might seem like a 200% decrease. But not so — because the old/original value is now different, has changed from $300 to $100. Thus: 100 (new) – 300 (old) / 300 (old) x 100. Which is -200/300 x 100; which is ‑66.66… Or a ~67% decrease.

Moral of the story: for real-world financial stuff, a percent decrease can never be greater than 100% — because 100% represents a (minimum) zero dollar amount.

Or maybe not… Stable genius and Wharton School of business grad, D. Trump, thinks the price of goods can be reduced by hundreds to thousands of percent. So what do I know?

Trump’s mathematically impossible promise to cut drug prices by ‘1,000%’​

https://www.cnn.com/2025/09/23/politics/fact-check-drug-prices-trump

BUT........maybe Trump is on to something us mere mortals don't or can't comprehend. Maybe he's saying that if you pay $100 for a prescription, we will get paid $900. 100%of $100 is $100. $100 times 10 (1,000%) is $1,000 so $100-$1,000 is -$900 or a $900 credit for us.

Ya think he meant that???

Bottom line is that we all need to start spending more money on drugs.....