Thermal Expansion of brass rod

[lackos]

Homework Statement

A student measures the length of a brass rod with a steel tape at 20.0°C. The reading is 80.00 cm. What will the tape indicate for the length of the rod when the rod and the tape are at each of the following temperatures?
a) -18.0°C

Homework Equations

(delta)L=a*L*(delta)T.where a for brass is 19e-6, and steel is 11e-6

The Attempt at a Solution

i sarted by finding the change in the increment of a cm on the steel tape using the the above equation and then finding the expansion for a cm of brass at the temperature. multipplied it by the original measurement, then added the resulting value to the measuremnt. however I am not sure if this is right

 

[rock.freak667]

Yes that would be correct. Just make sure your value for ΔL is negative, since your change in temperature is negative.