Answer 1

C.P. of 20 articles = S.P. of 16 articles.

Let C.P. of 1 article = Rs. 1

C.P. of 20 articles = Rs.20

and C.P. of 16 articles = Rs.16

S.P. of 16 articles = Rs.20 ........[S.P. of 16 articles = C.P. of 20 articles]

Gain = Rs.20 – Rs.16 = Rs.4

Gain% =`4/16xx100`

`=(4xx100)/16`

= 25%