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## Homework Statement

the difference in length between an aluminium rod and a copper rof at 0 degreeC is 2cm. If they have the same difference in length at any temperature difference, what are the length of the 2 rods at 0 degreeC.?

Al - expansivity = 20*10^-4 K^-1

Cu- expansivity= 15*10^-6 K^-1

## Homework Equations

alpha inversely proportional to the initial length

## The Attempt at a Solution

i divided the expansivities of the two rods and made it equal to the ratio of theinitial lengths of the rods and got the length of the Al rod as 6 cm and the Cu rod as 8 cm. Which is the answer the school teacher said is correct. I can't understand why it can't be the other way around.