Answer:
50 cm
Step-by-step explanation:
Let the increase i temperature of the metal rod is ΔT and the coefficient of linear expansion of the material of metal rod be ∝.
By use of the formula of linear expansion,

.... (1)
Let the expansion in length of rod is ΔL.
So,
.... (2)
Dividing equation (2) by equation (1), we get

ΔL = 0.5 m = 50 cm