WBCS Mains 2020 Official Paper-VI

$8$ men or $12$ women can do a piece of work in $20$ days. The number of days needed to complete the job, if $10$ men and $15$ women are employed to do the same piece of work is:

Raju invested $\text{Rs. }15,000$ in two parts. One part at $8\%$ and the other at $12\%$ per annum. His total annual income from interest is $\text{Rs. }1640$. The ratio of the two parts respectively is:

If a sum of money doubles itself at compound interest in $12$ years, in how many years will it become four times?

Successive discounts of $x\%$ and $y\%$ are equivalent to a single discount of:

Gold and Copper are heavier than water by $19$ and $9$ times respectively. In what proportion should they be mixed to form an alloy so that it will be heavier than water by $15$ times?