Answer: D) 14 min 40 sec. Explanation: Part filled in 4 minutes = 4(1/15 + 1/20) = 7/15   Remaining part = 1 - 7/15 = 8/15   Part filled by B in 1 minute = 1/20   1/20 : 8/15 :: 1 : k   k = (8/15 )x 1 x 20 = 10( 2/3) min = 10 min 40 sec.   The tank will be full in (4 min. + 10 min. 40 sec) = 14 min 40 sec.

Answer: D) Refraction of light & Total Internal Reflection of light Explanation: A Mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky. It is caused due to Total internal Reflection. It is an optical illusion observed in deserts or hot summer days due to which a person sees a pond of water some distance ahead of him in which the surrounding objects appear inverted. How Mirage Forms:: 1. The temperature of other layers of atmosphere goes on decreasing as we go up.2. Therefore density and refractive index of air changes as one goes up.3. Thus a ray of light,gets refracted more and more away from the normal.4. At a particular angle when a ray of light exceeds critical angle, total internal reflection takes place and ray of light gets reflected in the same medium.5. when the reflected ray reaches our eye, it appears as coming from tree or sky .6. Hence the inverted image of tree creates an impression from a pond of water.

Answer: C) Rs. 12,800 Explanation: 16x8 : Px4 = 5:2 P = 12.8 => Rs.12,800

Answer: D) 48 sec Explanation: Relative speed = 60 + 90 = 150 km/hr. = 150 x 5/18 = 125/3 m/sec. Distance covered = 1.10 + 0.9 = 2 km = 2000 m. Required time = 2000 x 3/125 = 48 sec.

Answer: A) +6 Explanation: We will rewrite the formula as an equation. 2K + 2Cr + 7O = 0 The zero comes from there being no overall charge on the compound. Each oxidation number is represented by the element's symbol. Since this compound is not a peroxide or superoxide, the oxidation value for O is -2 K being in group 1 has a +1 charge and therefore has an oxidation number of K is +1 Now, by putting known values in we have: 2(+1) + 2(Cr) + 7(-2) = 0 2 + 2Cr -14 = 0 2Cr = +12 Cr = +6.

Answer: C) Sublimation Explanation: Sublimation is a process when a solid changes directly into gas instead changing into liquid first. Dry ice is an example of Sublimation process because it doesn't change into liquid CO2 and directly change into gaseous CO2 when heated.   Hence, Dry ice is an example of Sublimation process.

Answer: C) 6 days Explanation: From the given data, 12 children 16 days work,One child’s one day work = 1/192. 8 adults 12 days work,One adult’s one day’s work = 1/96. Work done in 3 days = ((1/96) x 16 x 3) = 1/2 Remaining work = 1 – 1/2 = 1/2 (6 adults+ 4 children)’s 1 day’s work = 6/96 + 4/192 = 1/12 1/12 work is done by them in 1 day. 1/2 work is done by them in 12 x (1/2) = 6 days.

Answer: B) U Explanation: The letters move 2, 2, 3, 3, 4, 4, ... steps forward.