[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 425

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solve a square equation in the numerator.

you will have in the numerator (2-x)*(1-3x)

by cutting with the denominator (1-3x)

- you get the identity

 
Secondly, it can be solved by simple column division (it is difficult to judge which grade your pupil is in, but I think it is already taught in high school)
 

Challenging mathematicians. The problem was given at school to my friend's 12-year-old son. Interestingly, none of the 5th graders solved it.

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The problem is from the field of mathematics:


There is a masonry mesh with a number of cells horizontally and vertically equal to A. All cells are square. Each cell has length and width Z. You have to find the number of cells A if you know that workers have spent X metres of steel rod for the production of the grid. (The solution of the problem should be a formula for calculating A based on Z and X.)

Note (from me): the diameter of the rod is neglected, the rods are welded overlapping, all the wasted materials went to make the mesh.


 

my answer is a little bit the other way round.

how many wires X is needed to make the required number of cells A, if cell size Z is known

X=2*Z*(A^2+A)

But the ratio is obtained. From here you can express A.

But this is probably not a solution for 5th grade.

 
sergeev:

Yes, I got it backwards too. But how to flip it - I'll be honest, I couldn't do it.
 
Richie:

Yes, I got it backwards too. But how to reverse it - I can't tell you honestly, I couldn't.
And in life no one probably uses search A. On the contrary, X is interesting (costs)
 
sergeev: and in real life no one probably uses search A. On the contrary, X is interesting (costs).
That's the trick. Often, having gone one way, we can not go it in the opposite direction. But that's philosophy :)
 
Adding numbers with different powers is a formula. If you add a to the square and a to the first, then A itself can be derived.
 

if you graph a parabola y=x^2+x, then knowing y=X/2*Z you can look for x, i.e. A


 
drknn:
Adding numbers with different powers is a formula. If you add a to the square and a to the first, then A itself can be derived.
I don't think that's the answer for 5th grade.
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