The Maths and Science Thread - Collection of Problems and Facts

[Dipak]

For me, nothing can get easier than the method I posted. Possibly because I have been using it for years and have become quite used to it now.

agree to that but it's great to learn more and more new and easy methods. cant wait for varun's second update.

 

[Varun]

The magic of mental maths

Made my second post.

 

[Meet]

Hehe!
Same concept.
Anyways good find, Varun.
Great going so far, keep em coming.

 

[Chewie]

:P

I know where this fails but can you figure it out?

 

[P Squared]

I can't find anything wrong in it lol

 

[Gaurav_7]

The squares just don't cancel. I mean it will be 5-(9/2)= -{4-(9/2)}

 

[Meet]

I can't find anything wrong in it lol

Same here, lol.

The squares just don't cancel. I mean it will be 5-(9/2)= -{4-(9/2)}

It can if we have squares on both the side.

 

[Varun]

Just about what User said.

If (5-9/2)^2 = (4-9/2)^2, then it can be resolved into two cases of which only (or at least?) one must be right.

1. 5-9/2 = 4-9/2
2. 5-9/2 = - (4-9/2) or - (5-9/2) = (4-9/2) (Same thing really.)

As it might be obvious, the second condition solves the apparent paradox.

 

[6ry4nj]

Same here, lol.
It can if we have squares on both the side.

User and Varun are correct. a^2 = b^2 does not mean that a = b, because it is also true if a = -b, as in this case.

 

[Chewie]

Took me a while to figure it out as well

 

[Gaurav_7]

It can if we have squares on both the side.

Don't worry, I've seen so many students doing this same mistake and ending where the above equation did.

We don't just cancel anything at all. We always take it to the other side. Big difference really as shown in the above case.

 

[AbhishekS]

It can if we have squares on both the side.

No, you can't.

If we could cancel the squares, it would mean that 2=-2 or 5=-5, etc. In short, n would be equal to -n (where n is any number).

 

[Meet]

Yeah got it
It can be if we have cubes though.

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I know where this fails but can you figure it out?

Took me a while to figure it out as well

 

[Chewie]

I posted it after I had figured it out

 

[Varun]

The magic of mental maths: The third post

Updated the blog with my third post.