Riya purchases some pen @7 pen for Rs.5 and he sells all the pen @5 p…

             Price    :    Qty

Buy :        5      :      7             ......(i)

Sell :        7      :      5             ......(ii)

(i) × 5 & (ii) × 7, to make the equal quantity.

             Price    :     Qty

Buy :      25      :      35

Sell :      49      :      35

Here,

C.P. of 35 articles = Rs.25

S.P. of 35 articles = Rs.49

Profit = 49 - 25 = Rs.24

Hence,

Profit percent = \(\frac{24}{25}\) × 100% = 96%