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Math and logic riddle thread
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↑  ChanieMommy  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:15 pm
Tamari wrote:
Alice and Barbara together can finish a project in 3 hours.
Barbara and Cindy together can finish the same project in 4 hours.
Alice and Cindy together can finish it in 6 hours.
How long will it take them to finish this project if they all three work on it together? (Considering that everyone consistently works at her own pace)


My answer is:
Hidden: 

160 min or 2h40
So Cindy is the lazybone... without her, it just makes 20 min difference...
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:21 pm
ExtraCredit wrote:
Ok now this is hard but doable. Thanks! Let’s see...
Hidden: 

I think 68/34 but it’s an estimate


Nope
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:25 pm
malki2 wrote:
Nope

Right. Did it with calculator now and I’m off by a few digits.
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↑  ChanieMommy  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:29 pm
tothepoint wrote:
I’m blank as how to go about solving this Scratching Head


I did it in an amateurish way...

24p - the work necessary to complete the project. (I took 24p and not p, because you can divide 24 by 3, 4 and 6, so it makes calculation easier)

a - work Alice does per hour
b- work Barbara does per hour
c - work Cindy does per hour

Hidden: 

24p = 3a +3b = 4b + 4c = 6a + 6c

24p = 3a + 3b
3a = 24p - 3b
a = 8p - b

24p = 6a + 6c
6a = 24p-6c
a = 4p - c

24p = 4b + 4c
b = 6p-c

8p-b = a = 4p-c
8p-(6p-c) = 4p -c
2p + c = 4p -c
2c = 2p
c =p

b = 6p-c = 6p-p
b = 5p

a =4p-c = 4p-p
a = 3p

So in 1h, all three together achieve p +3p + 5p = 9p

To complete the whole work, they need 24 p, so the time they need is 24/9 hours, which is 8/3 hours, which is 8*20 min, which is 160 min or 2h40...
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:32 pm
ChanieMommy wrote:
I did it in an amateurish way...

24p - the work necessary to complete the project. (I took 24p and not p, because you can divide 24 by 3, 4 and 6, so it makes calculation easier)

a - work Alice does per hour
b- work Barbara does per hour
c - work Cindy does per hour

Hidden: 

24p = 3a +3b = 4b + 4c = 6a + 6c

24p = 3a + 3b
3a = 24p - 3b
a = 8p - b

24p = 6a + 6c
6a = 24p-6c
a = 4p - c

24p = 4b + 4c
b = 6p-c

8p-b = a = 4p-c
8p-(6p-c) = 4p -c
2p + c = 4p -c
2c = 2p
c =p

b = 6p-c = 6p-p
b = 5p

a =4p-c = 4p-p
a = 3p

So in 1h, all three together achieve p +3p + 5p = 9p

To complete the whole work, they need 24 p, so the time they need is 24/9 hours, which is 8/3 hours, which is 8*20 min, which is 160 min or 2h40...


As long as it works!
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↑  ChanieMommy  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:36 pm
ExtraCredit wrote:
Silly Silly
Never mind!


You have
A + b =40/h
B + C = 30/h
A + C = 20/h

So if you count them all together, you have.

A + B + B + C + A + C = 40+30+20/h

2A + 2B + 2C = 90/h
2(A + B + C) = 90/h
Now you divide both sides by 2:
A + B + C = 45/h

so together they produce 45 per hour, but you need 120
120/45 = 8/3 = 2h40
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↑  ChanieMommy  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:43 pm
malki2 wrote:
Ok here’s something:

To what food do you do the following, in the following order?
1. Throw away the outside
2. Cook the inside
3. Eat the outside
4. Throw away the inside

Hidden: 


Corn? Throw away the husk, cook the corn on the cob, eaat the corn,throw away the cob (or make a pipe from it)
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:45 pm
When is a stick a king?
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:45 pm
Why was baby ant confused?
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:48 pm
malki2 wrote:
When is a stick a king?

Not sure which of yours was hardest today!
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 2:51 pm
ExtraCredit wrote:
Not sure which of yours was hardest today!


The first one wasn’t mine. I just answered it.
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:04 pm
malki2 wrote:
The first one wasn’t mine. I just answered it.

Alright so when is a stick a king?
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:04 pm
ExtraCredit wrote:
Why was baby ant confused?


This better not have to do with ants/aunts...
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:04 pm
ExtraCredit wrote:
Alright so when is a stick a king?


When it’s a Ruler!
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:04 pm
malki2 wrote:
This better not have to do with ants/aunts...

Why not?
Hidden: 

Because all his uncles were ants.
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:06 pm
malki2 wrote:
When it’s a Ruler!

Ohhhh brilliant. How can we get this king brilliant too?
Hidden: 

With a sharpener
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↑  malki2  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:07 pm
ExtraCredit wrote:
Why not?
Hidden: 

Because all his uncles were ants.


Thought so...

Now that we’re getting silly,

Where do kings keep their armies?
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↑  dankbar  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:09 pm
Because when she was born she was already an aunt & her nieces were older than her. Which is the reverse of natural sequencing
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↑  dankbar  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:11 pm
malki2 wrote:
When it’s a Ruler!


Or when he is on a totem pole ( like high up there methaphorically or as literal stick) ha! Ha!
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↑  ExtraCredit  ↓




 
 
    
 

Post Tue, Oct 13 2020, 3:14 pm
malki2 wrote:
Thought so...

Now that we’re getting silly,

Where do kings keep their armies?

In their sleevies?
I still need the answer to your last decent question. I’m lazy to try other options.
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