WBCS Mains 2020 Official Paper-VI

Avishek sells a book at a profit of $20\%$. If he had bought it at $20\%$ less and sold it for $\text{Rs. }18$ less, he would have gained $25\%$. The cost price of the book is:

If $a^2+b^2+c^2=ab+bc+ca$, then which one is correct?

Ram and Shyam solve a quadratic equation. Ram makes a mistake in the constant term and finds the roots as $5,-3$. Shyam makes a mistake in the co-efficient of $x$ and gets the roots as $1,-3$. The correct roots are:

$\text{Rs. }6000$ is divided among $40$ boys and some girls so that each boy gets $\text{Rs. }100$ and each girl gets $\text{Rs. }250$, then the number of girls is:

A man gets a simple interest of $\text{Rs. }3500$ on a certain principal at the rate of $10\%$ per annum in $5$ years. What compound interest will the man get on twice the principal in two years at the same rate?