Question

The ratio of land to water for the whole earth is $1:2$ and $2:3$ in the northern hemisphere. What is the ratio of land to water in the southern hemisphere?

• A. (a)$4:11$
• B. (b)$1:3$
• C. (c)$1:4$
• D. (d)$4:7$

Answer 1

The correct option is A (a)$4:11$

(a) For the whole earth land $=\frac{1}{1+2}=\frac{1}{3}$,
$water=\frac{2}{1+3}=\frac{2}{3}$
$\therefore Forthenorhternhemisphereland=\frac{2}{5}\times \frac{1}{2}=\frac{1}{5}$
$andwater=\frac{3}{5}\times \frac{1}{2}=\frac{3}{10}asnorthernhemisphere=\frac{1}{2}ofwholeearth$.
$\therefore southernhemisphere,land=\frac{1}{3}-\frac{1}{5}=\frac{5-3}{15}=\frac{2}{15}$
$Water=\frac{2}{3}-\frac{3}{10}=\frac{20-9}{30}=\frac{11}{30}$
$\therefore Requiredratioofland:waterinsouthernhemisphere=\frac{2}{15}:\frac{11}{30}=4:11$.