CAT (QA) PYQs

A jar contains a mixture of $175 \mathrm{ml}$ water and $700 \mathrm{ml}$ alcohol. Gopal takes out $10 \%$ of the mixture and substitutes it by water of the same amount. The process is repeated once again. The percentage of water in the mixture is now

A mixture P is formed by removing a certain amount of coffee from a coffee jar and replacing the same amount with cocoa powder. The same amount is again removed from mixture $P$ and replaced with same amount of cocoa powder to form a new mixture $Q$. If the ratio of coffee and cocoa in the mixture $Q$ is $16: 9$, then the ratio of cocoa in mixture $P$ to that in mixture $Q$ is

There are four bottles. Each bottle is known to contain only P or only I. They will be considered to be “collectively ready for despatch” if all of them contain only P. In minimum how many tests, is it possible to ascertain whether these four bottles are “collectively ready for despatch”?.