An area of 100 sq. cm on the map represents an area of 49 sq. km on the field. The R.F. of the scale to be used is
(a)$\frac{1}{10000}$
(b)$\frac{1}{20000}$
(c)$\frac{1}{49000}$
(d)$\frac{1}{70000}$
Answer
Answer (as printed): D
Explanation
An area of 49 sq. km is represented by an area of 100 sq. cm on the map. So, a distance of 7 km is represented by a length of 10 cm on the map. $$\therefore \quad \text { R.F. }=\frac{10 \mathrm{cm}}{7 \mathrm{km}}=\frac{10 \mathrm{cm}}{7 \times 10^{5} \mathrm{cm}}=\frac{1}{70000} .$$