A snowman is built by stacking three spheres with their centres aligned vertically. The spheres have radii of $10 \mathrm{~cm}, 20 \mathrm{~cm}$ and $30 \mathrm{~cm}$. How tall is the snowman?
(A) $90 \mathrm{~cm}$
(B) $100 \mathrm{~cm}$
(C) $110 \mathrm{~cm}$
(D) $120 \mathrm{~cm}$
(E) $130 \mathrm{~cm}$
The height of the snowman equals the sum of the lengths of the diameters of the three spheres. Since the radii of the spheres are $10 \mathrm{~cm}, 20 \mathrm{~cm}$ and $30 \mathrm{~cm}$, then the lengths of their diameters are $20 \mathrm{~cm}, 40 \mathrm{~cm}$ and $60 \mathrm{~cm}$.

Thus, the height of the snowman is $20 \mathrm{~cm}+40 \mathrm{~cm}+60 \mathrm{~cm}=120 \mathrm{~cm}$.

ANSWER: (D)