1)从15°C到60°C:0.002 x (60-15)= 0.09m 伸长0.09m
2)从60°C到5°C:0.002 x (60-5)= 0.11m 缩短0.11m
0.11 - 0.09 = 0.02m
答:最后长度比原长度缩短 0.02m