Length of the steel tape at temperature $T=27^{\circ} C , l=1 m =100 cm$

At temperature $T_{1}=45^{\circ} C ,$ the length of the steel $\operatorname{rod}, l_{1}=63 cm$

Coefficient of linear expansion of steel, $\alpha=1.20 \times 10^{-5} K ^{-1}$

Let $l_{2}$ be the actual length of the steel rod and $I$ be the length of the steel tape at $45^{\circ} C .$

$l^{\prime}=l+\alpha l\left(T_{1}-T\right)$

$\therefore l^{\prime}=100+1.20 \times 10^{-5} \times 100(45-27)$

$=100.0216 cm$

Hence, the actual length of the steel rod measured by the steel tape at $45^{\circ} C$ can be calculated as

$l_{2}=\frac{100.0216}{100} \times 63=63.0136 cm$

Therefore, the actual length of the rod at $45.0\,^{\circ} C$ is $63.0136 \,cm .$ Its length at $27.0\,^{\circ} C$ is $63.0 \,cm$