Sakshi can do a piece of work in 20 days. Tanya is 25% more efficient than Sakshi. The number of days taken by Tanya to do the same piece of work is:

Explanation:-

$$\eqalign{ & {\text{Ratio}}\,{\text{of}}\,{\text{times}}\,{\text{taken}}\,{\text{by}}\,{\text{Sakshi}}\,{\text{and}}\,{\text{Tanya}} \cr & = 125:100 \cr & = 5:4 \cr & {\text{Suppose}}\,{\text{Tanya}}\,{\text{Takes}}\,x\,{\text{days}}\,{\text{to}}\,{\text{do}}\,{\text{the}}\,{\text{work}} \cr & 5:4::20:x \cr & \Rightarrow x = \left( {\frac{{4 \times 20}}{5}} \right) \cr & \Rightarrow x = 16\,{\text{days}} \cr & {\text{Hence,}}\,{\text{Tanya}}\,{\text{takes}}\,{\text{16}}\,{\text{days}}\,{\text{to}}\,{\text{complete}}\,{\text{the}}\,{\text{work}} \cr}$$