Answer: C) 2.83 kmph Explanation: Given speed of the person = 8 1/2 = 17/2 kmphLet the speed of the stream = x kmphspeed of upstream = 17/2 - xspeed of downstream = 17/2 + xBut given that,2(17/2 - x) = 17/2 + x=> 3x = 17/2=> x = 2.83 kmph.

A Contact force is a force applied to a body by another body that is in contact with it. Contact force acts on a point of direct contact between the two objects. This force can either be continuous as a continuous force or can be momentary in the form of an impulse. Contact force is governed by Newton’s Laws. Examples :: Contact force is responsible for most of the interactions we experience in the daily life. 1. Writing your name with a pen, pushing a car up a hill, lifting an object, etc... 2. Kicking a ball, hammering a nail, etc... are some of the everyday examples where contact forces are at work. In the first case, the force is continuously applied by the person on the car or pen or an object while in the second case the force is delivered in a short impulse.   Contact forces are often decomposed into orthogonal components one perpendicular to the surface in contact called the normal force, and one parallel to the surface in contact, called the friction force.

Answer: D) 91 Explanation: Here in the given numbers 91 is a Composite number. Since it has factors of 7 and 13 other than 1 and itself.   Composite Numbers : A composite number is a positive integer which is not prime (i.e., which has factors other than 1 and itself). Examples :: 4, 6, 8, 12, 14, 15, 18, 20, ...

We can make an equation: 3(100000 + x) = 10x+1 (Why? Well, adding 100000 puts a 1 at the front of a five-digit number, and multiplying by 10 and adding 1 puts a 1 at the end of a number) Solving this gives: 10x+1 = 3(100000 + x) 10x+1 = 300000 + 3x 10x = 299999 + 3x7x = 299999x = 299999/7 = 42857 The answer is 42857 (142857 is three times smaller than 428571).

Answer: D) 60/11 Explanation: A can complete the work in 12 days working 8 hours a day => Number of hours A can complete the work = 12×8 = 96 hours  => Work done by A in 1 hour = 1/96   B can complete the work in 8 days working 10 hours a day => Number of hours B can complete the work = 8×10 = 80 hours  => Work done by B in 1 hour = 1/80   Work done by A and B in 1 hour = 1/96 + 1/80 = 11/480  => A and B can complete the work in 480/11 hours   A and B works 8 hours a day. Hence total days to complete the work with A and B working together  = (480/11)/ (8) = 60/11 days

Answer: C) Red Explanation: The visible colors from Longest wavelength to Shortest wavelength are :: Red, Orange, Yellow, Green, Blue and Violet.                     Red > Orange > Yellow > Green > Blue > Violet.   1. Infrared radiation has a longer wavelength than visible Red light.   2. Ultraviolet radiation has a shorter wavelength than the visible violet light.    3. The white light is a mixture of the colors of the visible spectrum.