CAT (QA) PYQs

A person buys tea of three different qualities at Rs. $800$, Rs. $500$, and Rs. $300$ per kg, respectively, and the amounts bought are in the proportion $2: 3: 5$. She mixes all the tea and sells one-sixth of the mixture at Rs. $700$ per kg. The price, in INR per kg, at which she should sell the remaining tea, to make an overall profit of $50\%$, is

A solution, of volume $40$ litres, has dye and water in the proportion $2: 3$. Water is added to the solution to change this proportion to $2: 5$. If one-fourths of this diluted solution is taken out, how many litres of dye must be added to the remaining solution to bring the proportion back to $2: 3$?

A $20 \%$ ethanol solution is mixed with another ethanol solution, say, $S$ of unknown concentration in the proportion $1:3$ by volume. This mixture is then mixed with an equal volume of $20 \%$ ethanol solution. If the resultant mixture is a $31.25 \%$ ethanol solution, then the unknown concentration of $S$ is