Two types of tea costing Rs. 180/kg and Rs. 280/kg. In what ratio should these be mixed so that obtained mixture sold at Rs. 320/kg to earn a profit of 20% is ?

Answer: Option D

According to the question,
Selling price of the mixture = Rs. 320, Gain = 20%
∴ Cost price of the mixture
$$\begin{array}{rl}& =320\times \frac{100}{120}\\ & =\text{Rs}\text{. }\frac{800}{3}\end{array}$$
Now using alligation method

$$\begin{array}{rl}& \text{Ratio of quantity }\\ & \to 40:260\\ & 2:13\end{array}$$