Question

the length of a steel rod is 10 centimetre longer than that of brass rod if this difference in their length is to remain the same at all temperature then the length of a brass could be​

Answer 1

 Let Ls and Lb be the lengths of steel and brass rods respectively.  

The difference in the length remains constant if,

So, the concept lies here is strain or change in length of both the material will be constant.

So, In mathematical terms:

Strain or Delta (L) = Ls(αs)T = Lb(αb)T , so the temp will cancel out.

& we get,

Ls / Lb = αs/αb        ...(1)   where, α = coefficient of Thermal expansion

Also,               Ls- Lb = 10               ...(2)  

From (1) and (2), u will the answer.

Put the values of coefficient of Thermal expansion, I am u will get the answer.

 If any more explanation needed, feel free to ask !

Hope I helped :)

Answer 2

see the attachment

i have solved it using the difference in their length as 5 cm insted of 10 cm

the procedure xill remain same just replace 5 by 10cm in ur question