Answer: C) 042 Explanation: From all the hints given,  only 042 satisfies and it unlocks the key.

Answer: A) A Explanation: The quadratic equation whose roots are reciprocal of 2x2+5x+3=0 can be obtained by replacing x by 1/x.   Hence, 2(1/x)(1/x)+ 5(1/x) + 3 = 0   => 3x2+5x+2=0

Answer: B) Oxygen Explanation: Rust forms when oxygen reacts with chemicals in rocks, and that is often the case with many other elements in general. Like a copper nail being exposed to the air will rust.

An English word with five letters in which if you remove the last four letters, still pronounced the same is QUEUE.

Answer: C) Covalent Explanation: Covalent type of bonding joins the two hydrogen atoms. Hydrogen atoms in compounds such as H2 and H2O are joined to the molecule with covalent bonds. This is where electrons are shared between the atoms in order to fill there valence shells.

Answer: A) 12 Explanation: We have 12 months.   In every month we get 28 or more days.    So that implies we get 28 days in each and every month.

Answer: D) 140 mts Explanation: Speeds of two trains = 30 kmph and 58 kmph => Relative speed = 58 - 30 = 28 kmph = 28 x 5/18 m/s = 70/9 m/s Given a man takes time to cross length of faster train = 18 sec   Now, required Length of faster train = speed x time = 70/9  x  18 = 140 mts.

Answer: C) 1.8288 Explanation: One fathom = 1.8288 meters = 6 feet A fathom is a unit of length used especially for measuring the depth of water.