Both rods of same length, material and axis sectional area so their thermal conductivities (k) would be $be same
also, thermal resistance
Pm=LKA ⇒R1R2=K2K1 [K→ conductivity in series / parallel]
also thermal transfer
ΔQΔt=ΔTR [ΔQ= Heat transformed $\Delta T: Temperature difference]
That mass for same ΔQ & ΔT
Δ tαR t(2) [Δt= time taken]
From (1) & (2) gives
Δt1Δt2=R1R2=K2K1 given Δt1=125
In parallel connection K1=2K But in series K2=K/2 so:-
Δt1Δt2=K/22K=14⇒Δt2=4Δt1
=4×12=48