WBCS Mains 2019 Official Paper-VI

If $10$ men can do a piece of work in $18$ days, in how many days can $12$ men do it?

Present price of a machine is Rs. $2p$ and if the price of the machine decreases by $2r\%$ in each year, the price of the machine after $2n$ years will be:

A person deposited Rs. $100$ in a bank and got the amount Rs. $121$ for two years, the rate of compound interest per annum is:

Find the rate of compound interest per annum, so that the amount on Rs. $400$ for $2$ years becomes Rs. $441$.

If a sum of money doubles itself at a fixed rate of compound interest per annum in $n$ years, find in how many years it will become four times.