# A brass doorknob has a density of 8.0 grams per cubic centimeter and a

A brass doorknob has a density of 8.0 grams per cubic centimeter and a volume of 6.5 cubic centimeters. What is its mass?

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Provere
Step 1
Volume of sphere:
$$\displaystyle{v}={\frac{{{4}}}{{{3}}}}$$ or $$\displaystyle{r}^{{{3}}}$$
where $$\displaystyle{r}=\text{radius of sphere}$$
Step 2
Given diameter of sphere $$\displaystyle{d}={2}{c}{m}$$
$$\displaystyle{r}={\frac{{{d}}}{{{2}}}}={\frac{{{2}}}{{{2}}}}={1}{c}{m}$$
Now, volume of sphere
$$\displaystyle={\frac{{{4}}}{{{3}}}}$$ or $$\displaystyle{r}^{{{3}}}$$
$$\displaystyle={\frac{{{4}}}{{{3}}}}$$ or $$\displaystyle{\left({1}\right)}^{{{3}}}$$
$$\displaystyle={\frac{{{4}}}{{{3}}}}\times{3.14}$$
$$\displaystyle={4.186667}$$
Volume of sphere
$$\displaystyle\approx{4.19}$$ cubic centimeters.