The price of $1kg$ of sardines is $Rs 40$ and swordfish is $Rs 60$. Rohit sold $6kg$ swordfish. Rim earned as much money as Rohit. How many  $kg$ of Sardines did Rim sell?

Given:

Price of $1 kg$ Swordfish $= Rs 60$

Price of $1kg$ Sardines $=Rs 40$

Quantity of Swordfish sold by Rohit $=6kg$
To find: Quantity of Sardines sold by Rim if both earned the same amount of money
Price of $6kg$ Swordfish $=6\times 60=Rs 360$
Money earned by Rohit $=Rs 360$

Since money earned by Rim and Rohit is equal.
So money earned by Rim $=Rs 360$
Hence, the amount of Sardines sold by Rim  $=\frac{360}{40}=9kg$

Hence, Option B is the correct answer.