A man sells two articles for Rs. 2640 each. He gained 20% on the first and lost 12% on the second. Find his total gain or loss in the transaction

$\begin{array}{l}SPof2articles=2640\times 2=5280\\ 1^{st}at20\%profit\\ SoCPof{1}^{st}article\\ cp=2640\times \frac{100}{120}\\ cp=2200\\ CPof{1}^{st}article=2200\\ \end{array}$

$$\begin{gathered} cp of 2nd article=2640\times \frac{100}{88} \\ cp of 2nd article=3000 \end{gathered}$$

total cp=2200+3000=5200

profit%=$\frac{sp-cp}{cp}\times 100\%$

$$\begin{gathered} =\frac{5280-5200}{5200}\times 100\% \\ =\frac{80}{5200}\times 100\% \\ =\frac{20}{13}\% \\ =1\frac{7}{13}\% \end{gathered}$$