linear expansion?

Question

the concorde is 62 m long when its temperature is 23 degrees C. in flight, the outer skin of this supersonic aircraft can reach 105 degrees C due to air friction. the coefficient of linear expansion of the skin is 2.0 X 10^-5 (C-degrees)^-1. find the amount by which the concorde expands?

Answer 1

62*2x10^-5*82 m = 10.168 mm

Answer 2

∆L = 62(2.0 X 10^-5)(105 - 23)
∆L = 10.168 cm

Answer 3

expansion in length= L*a* dt where dt = rise in temp, a = coeff of expansion, L = initial length