The weight of a metal block of size 5 cm by 4 cm by 3 cm is 1 kg.

The weight of the metal block of dimension $5 \mathrm{~cm} \times 4 \mathrm{~cm} \times 3 \mathrm{~cm}$ is $1 \mathrm{~kg}$.

Its volume $=$ length $\times$ breadth $\times$ height $=(5 \times 4 \times 3) \mathrm{cm}^{3}=60 \mathrm{~cm}^{3}$

i. e., the weight of $60 \mathrm{~cm}^{3}$ of the metal is $1 \mathrm{~kg}$

Again, the dimension of the other block which is of same metal is $15 \mathrm{~cm} \times 8 \mathrm{~cm} \times 3 \mathrm{~cm}$.

Its volume = length $\times$ breadth $\times$ height $=(15 \times 8 \times 3) \mathrm{cm}^{3}=360 \mathrm{~cm}^{3}$

$\therefore$ The weight of the required block $=360 \mathrm{~cm}^{3}$

$=6 \times 60 \mathrm{~cm}^{3}\left(\because\right.$ Weight of $60 \mathrm{~cm}^{3}$ of the metal is $\left.1 \mathrm{Kg}\right)$

$=6 \times 1 \mathrm{~kg}$

$=6 \mathrm{~kg}$