The fun problem thread

Let your brain have some fun with these user-submitted brain games.
Snake Productions
Posts: 31
Joined: Sat Jan 12, 2019 11:27 am

Re: The fun problem thread

Post by Snake Productions » Sat Jan 12, 2019 11:34 am

Adriel wrote:
Sat Jan 12, 2019 11:33 am
Snake Productions wrote:
Sat Jan 12, 2019 11:32 am
Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
y = 3/(2x^2)?

Edit: I mean what 2/3.
OK, then how come when we substitute 3 back into the equation we just found (y = 2/(3x^2)), y isn't equal to 2?
If you substitute 1/x^2 = 3, it does.

ALEX
Site Admin
Posts: 99
Joined: Sat Jan 12, 2019 8:07 am

Re: The fun problem thread

Post by ALEX » Sat Jan 12, 2019 11:35 am

Ollie wrote:
Sat Jan 12, 2019 11:31 am
Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
Is it y = 2/(3x^2)?
Hmm... How did you get this answer?

(Sorry, I'm a bit stupid.)

What is the value next to the x axis supposed to represent? And what is the default value?

Adriel
Posts: 33
Joined: Sat Jan 12, 2019 9:23 am

Re: The fun problem thread

Post by Adriel » Sat Jan 12, 2019 11:36 am

Snake Productions wrote:
Sat Jan 12, 2019 11:34 am
Adriel wrote:
Sat Jan 12, 2019 11:33 am
Snake Productions wrote:
Sat Jan 12, 2019 11:32 am


y = 3/(2x^2)?

Edit: I mean what 2/3.
OK, then how come when we substitute 3 back into the equation we just found (y = 2/(3x^2)), y isn't equal to 2?
If you substitute 1/x^2 = 3, it does.
OK thanks man, I get it now.
ALEX wrote:
Sat Jan 12, 2019 11:35 am
Ollie wrote:
Sat Jan 12, 2019 11:31 am
Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
Is it y = 2/(3x^2)?
Hmm... How did you get this answer?

(Sorry, I'm a bit stupid.)

What is the value next to the x axis supposed to represent? And what is the default value?
Find the gradient of the line, and then just multiply it by 1/x^2. :)

Ollie
Posts: 34
Joined: Sat Jan 12, 2019 9:36 am

Re: The fun problem thread

Post by Ollie » Sat Jan 12, 2019 11:38 am

ALEX wrote:
Sat Jan 12, 2019 11:35 am
Ollie wrote:
Sat Jan 12, 2019 11:31 am
Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
Is it y = 2/(3x^2)?
Hmm... How did you get this answer?

(Sorry, I'm a bit stupid.)

What is the value next to the x axis supposed to represent? And what is the default value?
What do you mean by 'default value'?

exabyte
Posts: 46
Joined: Sat Jan 12, 2019 8:39 am

Re: The fun problem thread

Post by exabyte » Sat Jan 12, 2019 11:40 am

Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
That graph offends me to the core of my being, but here is the worked out explanation:

The graph shows that y is a linear function of 1/x^2, that is, y = k * 1/x^2 (presumably the graph starts at zero, otherwise the question is unanswerable)

The graph also says that when 1/x^2 = 3, y = 2,

so 2 = k * 3 => 2/3 = k,
so y = (2/3) * (1/x^2) = 2/(3x^2).

ALEX
Site Admin
Posts: 99
Joined: Sat Jan 12, 2019 8:07 am

Re: The fun problem thread

Post by ALEX » Sat Jan 12, 2019 11:41 am

Adriel wrote:
Sat Jan 12, 2019 11:36 am
Snake Productions wrote:
Sat Jan 12, 2019 11:34 am
Adriel wrote:
Sat Jan 12, 2019 11:33 am


OK, then how come when we substitute 3 back into the equation we just found (y = 2/(3x^2)), y isn't equal to 2?
If you substitute 1/x^2 = 3, it does.
OK thanks man, I get it now.
ALEX wrote:
Sat Jan 12, 2019 11:35 am
Ollie wrote:
Sat Jan 12, 2019 11:31 am


Is it y = 2/(3x^2)?
Hmm... How did you get this answer?

(Sorry, I'm a bit stupid.)

What is the value next to the x axis supposed to represent? And what is the default value?
Find the gradient of the line, and then just multiply it by 1/x^2. :)
exabyte wrote:
Sat Jan 12, 2019 11:40 am
Adriel wrote:
Sat Jan 12, 2019 11:30 am
There's a simple question in the picture attached. I want to see what you guys get. An answer by itself is fine, no working out or anything required.

Thanks.
That graph offends me to the core of my being, but here is the worked out explanation:

The graph shows that y is a linear function of 1/x^2, that is, y = k * 1/x^2 (presumably the graph starts at zero, otherwise the question is unanswerable)

The graph also says that when 1/x^2 = 3, y = 2,

so 2 = k * 3 => 2/3 = k,
so y = (2/3) * (1/x^2) = 2/(3x^2).
Ah, thanks guys, it makes sense now.
Ollie wrote:
Sat Jan 12, 2019 11:38 am
ALEX wrote:
Sat Jan 12, 2019 11:35 am
Ollie wrote:
Sat Jan 12, 2019 11:31 am


Is it y = 2/(3x^2)?
Hmm... How did you get this answer?

(Sorry, I'm a bit stupid.)

What is the value next to the x axis supposed to represent? And what is the default value?
What do you mean by 'default value'?
I got confused when looking at the axis.

By 'default', I meant the x axis, which was changed to 1/x^2.

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