Explanation:
you know that you can change and reform any equation by doing the same operation to everything on the left and on the right side of the "=" sign ?
that way you can change the appearance of terms and the locations of variables or constants without changing the expressed balance.
this is like in a 2-bowl scale, where you can add or remove the same weight on both sides to keep the scale in balance.
and that is the principle, when we transform equations.
4.
V = RI
we want to have "I" alone on one side. so, what do we need to do ? a division by "R", of course.
again, it has to happen on both sides of the "scale" ...
V/R = I
I = 50/2.5 = 20 A (or amps)
5.
the area of a circle is
A = pi × r²
with r being the radius.
now, r should stand alone (and is the result of the other values). so, what do we need to do ?
well, first we divide both sides by pi :
A/pi = r²
and now ? how do we get r from r² ? we pull the square root (sqrt()) ! again, as always, both sides :
r = sqrt(A/pi)
r = sqrt(100/pi) = sqrt(31.83098862...) =
= 5.641895835... ≈ 5.64 mm