Answer :
tn=a+(n-1)d
1.8=1.2+60d
d=.001m=1mm
this is d difference in length
sum=n/2(a+tn)
=61/2*3
=91.5m
1.8=1.2+60d
d=.001m=1mm
this is d difference in length
sum=n/2(a+tn)
=61/2*3
=91.5m