R1=R0[1+α×100]=100.....(1) R2=R0[1+α×T]=200.....(2) On dividing we get
200
100
=
1+αT
1+100α
⇒2=
1+0.005T
1+100×0.005
⇒T=400∘C NOTE : We may use this expression as an approximation because the difference in the answers is appreciable. For accurate results one should use R=R0eα∆T