A merchant has 1000 kg of sugar, part of which he sells at 8% profit and the rest at 18% profit. He gains 14% on the whole. The quantity sold at 18% profit is:

Answer: Option C

By the rule of alligation, we have:

Ratio of 1^st and 2^nd parts
= 4 : 6
= 2 : 3
∴ Quantity of 2^nd kind
$$\begin{array}{rl}& =\left(\frac{3}{5}\times 1000\right)\text{kg}\\ & =600\text{kg}\end{array}$$