[tex]\large\boxed{\pink{\sf \leadsto He \ purchased \ the \ fan \ for \ Rs 700. }}[/tex]
Given that , a retailer makes a profit of 5% by selling a fan for Rs 735 . So let us take CP be x .
Now , here
[tex]\implies \red{\sf Profit \ made \ by \ retailer = 5\% }[/tex]
Here we assumed CP to be x , and profit % is 5% . So , its SP will be
[tex]\implies SP = CP + 5\% \ of \ CP \\\\\implies Rs 735 = x + \dfrac{5}{100}x \\\\\implies \dfrac{100x+5x}{100}= Rs 735 \\\\\implies \dfrac{105x }{100}= Rs 735 \\\\\implies x = \dfrac{735\times 100}{105} \\\\\underline{\boxed{\orange{\tt \implies x = Rs 700 }}}[/tex]