# Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 Help Me ! » Folding Papers » 2022-10-07 00:28:40

CurlyBracket
Replies: 1

Here's the question:

And here's what I did:

AB = 4

BN = x

In Δ ABN,

(16-x)² = 4² + x²

So, x = 15/2

AN = (16 - x²)
= 17/2

Now, area of ABNMD` = ABCD - ANM

= (4 * 16) - ((1/2) * (15/2 ) * 4)

= 64 - 15

= 49 cm²

Where am I mistaken?

## #2 Re: Introductions » New Member - Maths is a game » 2022-08-30 23:54:32

Hi mathscolor,

Welcome to the forum! I hope you have a good time here.

## #3 Re: Exercises » Non - Routine Algebra » 2022-08-30 21:06:05

Correct answer! And great explanation too.

Easy one now :

Question 7

There are 3 numbers.

The second is greater than the first by the amount the third is greater than the second.

The product of the two smaller numbers is 85.

The product of the two larger numbers is 115.

If the numbers are x, y, z with x<y<z then the value of (2x + y+ 8z) is?

## #4 Re: Exercises » Non - Routine Algebra » 2022-08-29 21:39:14

Ok, done. Thanks, phrontister.

Here’s the next one.

Question 6

The combined age of a man and his wife is six times the combined ages of their children.

Two years ago their united ages were ten times the combined ages of their children.

Six years hence their united ages will be three times the combined ages of the children.

How many children do they have?

## #5 Re: Exercises » Non - Routine Algebra » 2022-08-29 19:17:04

Then should I edit it to just say "Who won?"

## #6 Re: Puzzles and Games » Hangman 1 » 2022-08-28 17:00:37

I've seen an interesting trend. Most of my classmates use the latest apps and social networks (Discord, Insta, etc etc) but there's a growing population of people who have begun to quit them because they're 'getting too popular'!

It's as if the 'centralization' of the web will ultimately lead to its 'decentralization'.

Eh, people are complicated.

As for you're word, is there a 'T'?

## #7 Re: Exercises » Non - Routine Algebra » 2022-08-28 16:45:03

Hi phrontister,

I solved it like this. It's quite similar.

## #8 Re: This is Cool » Library of Babel » 2022-08-28 16:18:39

Bob wrote:

I'm not sure my brother would be happy to be described as lazy

Mycroft did his analysis sitting in an armchair.  Physically not much but mentally a tour de force.

Bob

Oopsies! I didn't think of it that way.

Then your brother, who's in the University of Edinburgh, is working on a mathematical fact checker?

That sounds really awesome.

## #10 Re: Help Me ! » Trigonometry Table » 2022-07-11 04:28:32

Ok, got it.

Then the known values for AP will be at 135, 225 and 315.

## #11 Re: Exercises » Compute the solution: » 2022-07-10 00:16:10

Hi,

P.S: The same question came in my exam today!

## #12 Re: Exercises » Non - Routine Algebra » 2022-07-10 00:10:05

I've got it now! Thanks for the help, Bob and Ganesh!

Here's another question. It's a bit different from the others. Flavours are the essence of life!

Question 5

Three teams of woodcutters have decided to organize a competition. The winner is the team who fells the maximum number of trees in the given time.

The first and third team together felled twice the number of trees felled by the second team.

The second and third team together felled three fold of the number of trees felled by the first team.

Who won? Or in the event of there being joint winners, who would then be named as such?

## #13 Re: Help Me ! » Trigonometry Table » 2022-07-09 23:43:28

Hi Bob,

A big THANK YOU!!

Okay, I'll answer the questions now.

(a) What is the largest that AP can ever be?

(b) What is the most negative it can be?

(c) In my image the angle POA is 45 degrees and we know the coordinates.  Just based on that and using symmetry for what other angles would you be able to give the distance AP?  You should be able to find three possible answers here, one between 90 and 180, and two more where the angle is over 180.

(d) If P goes al the way round and starts a second circle we could record the angle by using numbers over 360.  For example, P will be back to my image position when the angle of turn is 360 + 45 = 405.  What is the next angle when P is in this position?

(a) 1 unit.

(b) -1 unit.

(c) I'm not about this one. But I know the value for AP at 0, 90, 180 and 270.

(d) 405 + 360 = 765. Oh wait, that sort of explains the Trigonometry Table thing! I see now.

## #14 Re: Jokes » Fibonacci » 2022-06-27 02:20:19

Hi Phil,

I'll say this in ganesh's style:

Welcome to the forum!

Good joke

## #15 Re: Maths Is Fun - Suggestions and Comments » On improving the "Messaging" subsection of the Profile section » 2022-06-27 02:09:19

Hi,

I know this is a bit of an aside but still - it's surprising how dynamic the world of the internet is.

Personally,  I've never heard of these services mentioned above, with the sole exception of AOL, which we use as an inside joke among my friends to describe someone who just can't move on from the old,  lives in a shed with a cowboy hat - that sort of thing.

Today's mega giants - Discord, Reddit,  YouTube, Instagram,  Twitter even outlook or gmail! How long do they have?

I was a five year old when Skype and Yahoo were all the rage. Why did they stop? Why do any of these stop?

Is there a way to determine the decline of a certain app or website?

What are the factors behind this?

## #16 Re: Help Me ! » Trigonometry Table » 2022-06-27 01:55:28

Hi Bob,

That would be very kind of you.

I find most sources,  like textbooks,  to either ramble about really basic knowledge, OR to skip many parts in a bid to be faster.

## #17 Re: This is Cool » Library of Babel » 2022-06-27 01:51:42

Mycroft?  You mean Sherlock's brother,  who was the smarter of the two,  but too lazy to do anything?

## #18 Re: Puzzles and Games » Hangman 1 » 2022-06-12 03:22:28

Yes, it’s quite clear by reading the old posts that this very forum used to be a rather vibrant and lively place.

No ‘e’? Well, then, how about ‘a’?

## #19 Re: Exercises » Non - Routine Algebra » 2022-06-10 19:20:17

Ahoy there! I'm back!

Question 4

If x²+ 2x + 5 is a factor of x^4 + px² + q.

p, q =?

## #20 Re: Puzzles and Games » Hangman 1 » 2022-06-10 19:14:17

I'd be worried if anyone remembered a word after that long, because that'd mean they had nothing better to do!

I'm looking forward to your celebratory post!

Is there an 'E' in your word?

## #21 Re: Exercises » Non - Routine Algebra » 2022-05-20 18:03:11

Hi,

I was trying using this method:

I think it is almost the same method, just a little more direct.

## #22 Re: This is Cool » Library of Babel » 2022-05-17 22:27:01

Hi,

I'm not sure what the matter with the reply above is.

To read the post, consider click on Quote.

I wonder if there's a certain number of characters which the forum can allow in a single post?

The post was ok before, but I decided to put the image numbers in hide tags to facilitate scrolling, and then this happened.

## #24 Re: This is Cool » Library of Babel » 2022-05-17 18:40:43

Hi Mathegocart,

I remember adding a link to the website at the end of Post #1, but it seems to have disappeared. Thanks for mentioning it here!

Yes, a real life LOB would be incredibly impractical. I shouldn't be surprised if it doesn't fit in the area of Russia, with each building being the height of the Burj Khalifa.

All hail the Internet!

## #25 Re: Exercises » Non - Routine Algebra » 2022-05-12 19:49:29

Hi Bob,

Thank you, that makes sense.

Here's the next question:

Question 3

If n! has 4 zeroes at the end.

(n+1)! has 6 zeroes at the end.

Find the value of n.