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## Homework Statement

A concrete highway is built of slabs 12 m long (20°C). How wide should the expansion cracks be (at 20°C) between the slabs to prevent buckling if the range of temperature is -30°C to +32°C?

________ cm

## Homework Equations

change in L = L original * alpha * change in temp

sorry i dont have symbols and stuff

## The Attempt at a Solution

I've tried it one way so far.

Basically, I just found the difference between the higher temp and the highway temp, and solved that as one equation. Then i found the difference between the lower temp and the highway temp, and solved that as one equation. Then i added the two answers.

change in L = 12m * 1200e-6(our teacher gave us this for alpha) * (32-20) = .1728

change in L = 12m * 1200e-6 * (20-(-30)) = .72

then i got .8928 cm

any help?