A person bought two articles for Rs. 800and Rs. 1200. One he sold at a gain of 10%. How much did he sell the other to get a gain of 16% on the whole.

$\begin{array}{l}CPof{1}^{st} Article=800\\ CPof 2^{nd} Article=1200\\ Totalcp=1200+800=2000\\ s.p of 1st article=800\times \frac{110}{100}=880\\ s.p of 2^{nd}article=2320-880=1440\\ 1440-1200=240\\ \frac{240}{1200}\times 100=20\%\\ to get gain of 16 \% on the whole ,\\ he has to sell the other at a gain of 20\%\\ \end{array}$