Posted by sima on Wednesday, April 4, 2012 at 8:32am.
A steel rod of length 4 m is welded to the end of an aluminum rod of length 3 m (lengths measured at 23 °C). The combination rod is then heated to 198 °C. What is the length of the combination rod at 198 °C? (The linear expansion coefficients for steel and aluminum are 1.3 105 °C−1 and 2.2 105 °C−1, respectively. Enter your answer to three significant figures.)
I know the equation to be used is, delta length=(linear coefficient of expansion)(length)(delta temperature)
i am confused as to what to use for length on the right side of the equation, and what to subtract from delta length

physics  bobpursley, Wednesday, April 4, 2012 at 11:19am
Hmmm. Do it in two parts, steel expansion, and aluminum expansion, then add the two expansions.

physics  Anonymous, Wednesday, April 4, 2012 at 11:48am
What do i use for delta length?

physics  bobpursley, Wednesday, April 4, 2012 at 12:34pm
That is what you are solving for.
deltaLengthAl= coeff*changetemp*lengthorigAl
deltaLengFe= coeff*changetemp*lenghorigFe
Total changelenght= sum of above 
physics  Anonymous, Wednesday, April 4, 2012 at 2:34pm
it didn't give me the correct answer