Math and logic riddle thread

↑ pause ↓

Wed, Sep 23 2020, 10:42 am

doctorima wrote:

Maybe I'm just slow today, but I'm not getting it (even after seeing the hidden answer). Can you please explain?

Hidden:

↑ malki2 ↓

Wed, Sep 23 2020, 10:43 am

doctorima wrote:

Maybe I'm just slow today, but I'm not getting it (even after seeing the hidden answer). Can you please explain?

The beginning of the word סוף is the last letter of the word פנחס...
The end of the word סוף is the first letter
נח came into the middle of the word תבה

↑ malki2 ↓

Wed, Sep 23 2020, 10:45 am

pause wrote:

Huh?

The algae covered 0.0000019 square meters on the first day.

↑ pause ↓

Wed, Sep 23 2020, 10:49 am

malki2 wrote:

The algae covered 0.0000019 square meters on the first day.

Did you see my answer? I just calculated it and got 0.00000381469. I'm wondering if our methods were similar.

↑ malki2 ↓

Wed, Sep 23 2020, 10:52 am

pause wrote:

Did you see my answer? I just calculated it and got 0.00000381469. I'm wondering if our methods were similar.

Yes but your number is correct for day 2.

If you know how to do it on Excel, it’s pretty clear.

↑ pause ↓

Wed, Sep 23 2020, 10:54 am

malki2 wrote:

Yes but your number is correct for day 2.

Why? If Day 20 was 1, then day 19 was .5 so I needed to divide by 2 (or multiply by .5) another 18 times, no?

↑ malki2 ↓

Wed, Sep 23 2020, 10:58 am

pause wrote:

Why? If Day 20 was 1, then day 19 was .5 so I needed to divide by 2 (or multiply by .5) another 18 times, no?

Correct. And then you will get my answer.

↑ pause ↓

Wed, Sep 23 2020, 11:38 am

malki2 wrote:

Correct. And then you will get my answer.

Google's scientific calculator gives the answer I posted.

↑ malki2 ↓

Wed, Sep 23 2020, 11:49 am

pause wrote:

Google's scientific calculator gives the answer I posted.

↑ ChanieMommy ↓

Wed, Sep 23 2020, 1:06 pm

malki2 wrote:

1.91E-06 square meters

Yes! which would amount to 1,907 mm²

Thanks for your convicing excell table... indeed it is a bit confusing, but we have to divide 1024 by 2²⁹ to get the surface on day 1...

Pause you were right too, you can do 1:2¹⁹ or 0,5:2¹⁸, which also gives 1,907 * 10^-6

So on the first day, the algae would be just visible with the naked eye... the size of a louse or so...

amazing, isn't it?

↑ ChanieMommy ↓

Wed, Sep 23 2020, 1:16 pm

malki2 wrote:

Ok on to a new riddle. I’ll be unambiguous this time.

What weekly Parsha is described by the following 3 clues:

תחילת סוף סופה
סוף סוף תחילתה
ויבא נח אל התבה

That's a very nice one... I gave it over to the next generation, and they were enthralled! they loved it!

↑ pause ↓

Wed, Sep 23 2020, 3:33 pm

My filter doesn't let images through, so I'll have to do without the explanation.

↑ ChanieMommy ↓

Wed, Sep 23 2020, 3:38 pm

pause wrote:

My filter doesn't let images through, so I'll have to do without the explanation.

The table goes through all the days... you see each day with the surface, and it gets to 1,91 mm² for day 1... 3,81 mm² is the figure for day 2...

Also, I did 0,5 : 2¹⁸ and also got 1,907 * 10^-6

↑ pause ↓

Wed, Sep 23 2020, 4:31 pm

ChanieMommy wrote:

I don't understand the math here. Is this 0.5? What does the colon mean?

↑ ChanieMommy ↓

Wed, Sep 23 2020, 4:37 pm

pause wrote:

I don't understand the math here. Is this 0.5? What does the colon mean?

Yes, I mean 1/2

colon means "divided by"... don't you use this sign?

And I understand now how you got 3,81 mm²

You probably did 1:2¹⁸
but you have to do 1:2¹⁹ or 1/2 * 1/2¹⁸

↑ pause ↓

Wed, Sep 23 2020, 5:15 pm

ChanieMommy wrote:

Yes, I mean 1/2

colon means "divided by"... don't you use this sign?

And I understand now how you got 3,81 mm²

You probably did 1:2¹⁸
but you have to do 1:2¹⁹ or 1/2 * 1/2¹⁸

I use the / sign for "divided by"

So now I understand the discrepancy in answers. I did to the 18th power because 0.5 is already day 19, and Malki2 did say

Quote:

pause wrote:
Why? If Day 20 was 1, then day 19 was .5 so I needed to divide by 2 (or multiply by .5) another 18 times, no?

Correct. And then you will get my answer.

So wouldn't that translate into 0.5¹⁸? Why are you saying it should be 0.5¹⁹?

↑ ChanieMommy ↓

Wed, Sep 23 2020, 5:27 pm

pause wrote:

So wouldn't that translate into 0.5¹⁸? Why are you saying it should be 0.5¹⁹?

Because as you said yourself, it is 0.5 divided by 2¹⁸
or 1/2 times 1/2¹⁸
You have to count the 2 from the first 1/2 too... plus 18 more... so a total of 19

↑ pause ↓

Wed, Sep 23 2020, 7:10 pm

ChanieMommy wrote:

Because as you said yourself, it is 0.5 divided by 2¹⁸
or 1/2 times 1/2¹⁸
You have to count the 2 from the first 1/2 too... plus 18 more... so a total of 19

Yeah, ok, ok. Got it! I'm actually laughing at myself now. LOL

↑ doodlesmom ↓

Wed, Sep 23 2020, 7:20 pm

Can we get more logic riddles now please.....I’m really enjoying this thread FYI.