Diamonds are measured in carats, and 1 carat = 0.200 g. The density of diamond is 3.51 g /cm, what are the volume and density of the block? The sample is 4.5 carats

Well, we use the formula, $\text{density,}$ $\rho$ $=$ $\text{Mass"/"Volume}$.
$\text{Mass}$ $=$ $4.5 {\text{ carat"xx0.200*g*"carat}}^{-} 1$ $=$ $0.9 \cdot g$.
And $\text{Volume}$ $=$ $\frac{\text{Mass}}{\rho}$ $=$ $\frac{0.9 \cdot g}{3.51 \cdot g \cdot c {m}^{-} 3}$ $=$ $0.26 \cdot c {m}^{3}$.