Jawabanmu

2014-03-10T22:47:18+07:00
L = 60 m
ΔT= 70 C - 20 C = 50 C
= 0,00002/C

L = 40cm [1 + (0,00002/C)(50 C)]
L = 40 cm (1 + 0,00052)
L = 40 cm + 0,0692
L = 40,0792

Maaf kalau jawabannya salah :)
2014-03-10T23:02:00+07:00
ΔL = L[0] * α * ΔT
     = 40 * 0,00002 * 50
     = 0,0008 * 50
     = 0,04 cm

L = L[0] + ΔL 
   = 40 + 0,04 
   = 40,004 cm