A conical tent is to accommodate 11 persons such that each person occupies 4 m2 of space on the ground.

(b) 15 m

Suppose that the height of the cone is h m.

Area of the ground $=11 \times 4=44 \mathrm{~m}^{2}$

$\therefore \pi r^{2}=44$

$\Rightarrow r^{2}=\frac{44 \times 7}{22}=14$

Also, $\frac{1}{3} \pi r^{2} h=220$

$\Rightarrow \frac{1}{3} \times \frac{22}{7} \times 14 h=220$

$\Rightarrow h=\frac{220 \times 21}{22 \times 14}=15 \mathrm{~m}$

Hence, the height of the cone is 15 m.