How to Calculate the Length of a Copper Wire Based on Resistance?

[dramaqueen]

a copper wire 750ft long has resistance of 1.563. How long is a copper wire of the same cross-sectional area whose resistance is 2.605. Note: the resistance of these wire is proportional to their length.

attempted to solve:

750ft/1.563=x/2.605
then cross multiply
750 * 2.605 = 1953.750/1.563
= 1250 ft

can someone advise if I am right

thanks

 

[Mark44]

a copper wire 750ft long has resistance of 1.563. How long is a copper wire of the same cross-sectional area whose resistance is 2.605. Note: the resistance of these wire is proportional to their length.

attempted to solve:

750ft/1.563=x/2.605

You have set up the proportion correctly, but don't seem to understand what to do next.

then cross multiply

Your equation above has x in it. Where did it go?
What you want to do is to get x all by itself on one side of the equation. When you do this, you will have solved the equation.

Ignoring the units for the moment, you have 750/1.568 = x/2.605
What operation can you do to both sides of this equation so that x is by itself? DO NOT SAY cross multiply.