Linear Expansion related to area expansion

[student 1]

Homework Statement

An automobile windshild has dimensions of 60 cm by 150 cm. What minimum tolerance in mm is needed to prevent the windshield from breaking if the temperature changes by 200 degrees Farenheight? (The linear expansion coeffecient of galss is 9 x 10$$^{}-6$$
(C)^-1

Homework Equations

area expansion = Ai(Area expansion coefficient)(Change in Temp)
Area expansion coefficient=2(Linear expansion coefficient)

The Attempt at a Solution

I found my area to be 900,000 mm² The change in temperature 111 Degrees Celsius. but I'm not getting the right answer when I multiply 2(Linear expansion coefficient)
I'm getting a huge number for my final answer when it should be really small.

 

[Doc Al]

You don't need to consider anything beyond linear expansion. They are looking for an answer in mm.

 

[student 1]

So do I use the 60 mm or the 150 mm? I figured I was trying to over think it.

 

[Doc Al]

So do I use the 60 mm or the 150 mm?

Good question. Each dimension would have a different answer. If I had to pick, I'd go with the larger dimension. (Note that those measurements are in cm, not mm.)

 

[student 1]

ok, I'll try them both! Thanks!