When a women sells 20 articles for Rs. 160, there is 40% loss. How many articles should she sell for Rs. 240 in order to earn 20% profit ?

Given when she sells at Rs. 160 for 20 articles, she get 40% loss.

Then, to get 20% profit selling at Rs. 240 for let 'P' articles

=>  $\frac{\frac{160}{20}}{60}=\frac{\frac{240}{p}}{120}$

=> 120 x 160 x P = 20 x 70 x 240

=> P =  15 articles.