List of top Questions asked in WBJEE- 2013

An objective type test paper has $5$ questions. Out of these $5$ questions, $3$ questions have four options each $(A, B, C, D)$ with one option being the correct answer. The other $2$ questions have two options each, namely True and False. A candidate randomly ticks the options. Then the probability that he/she will tick the correct option in at least four questions, is

The sum of the series $\frac{1}{1\times2} ^{^{25}}C_{0} + \frac{1}{2\times3}^{^{25}}C_{1} + \frac{1}{3\times4} ^{^{25}}C_{2} + ......... + \frac{1}{26\times27} ^{^{25}}C_{25}$

The value of $1000\left[\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...... +\frac{1}{999\times1000}\right]$ is equal to

A mass $M$ at rest is broken into two pieces having masses $m$ and $(M-m)$. The two masses are then separated by a distance $r$. The gravitational force between them will be the maximum when he ratio of the masses $[m:(M-m)]$ of the two parts is

A biconvex lens of focal length $f$ and radii of curvature of both the surfaces $R$ is made of a material of refractive index $n_1$. This lens is placed in a liquid of refractive index $n_2$. Now this lens will behave like

Acid catalysed hydrolysis of ethyl acetate follows a pseudo-first order kinetics with respect to ester. If the reaction is carried out with large excess of ester, the order with respect to ester will be

For isothermal expansion of an ideal gas, the correct combination of the thermodynamic parameters will be

Water is flowing in streamline motion through a horizontal tube. The pressure at a point in the tube is $p$ where the velocity of flow is $v$. At another point, where the pressure is $p/2$, the velocity of flow is [density of water = $?$]

In diborane, the number of electrons that account for bonding in the bridges is

In borax the number of $B-O-B$ links and $B-OH$ bonds present are, respectively,