Answer: A) Total internal reflection Explanation: A periscope is an optical instrument that uses a system of prisms, lenses, or mirrors to reflect images through a tube.       Light from a distant object strikes the top mirror and is then reflected at an angle of 90 degrees down the periscope tube. At the bottom of the periscope, the light strikes another mirror and is then reflected into the viewer’s eye.   Hence, A periscope works by the principle of Total internal reflection.

Answer: B) A = 30000 B = 40000 C = 48000 Explanation: Compound ratio of A:B:CA:B = 3:4B:C = 5:6----------A:B:C = 15:20:24 We can divide Rs.118000 in this ratio. Share of A = 15/59 x 118000 = 30000 Share of B = 20/59 x 118000 = 40000 Share of C = 24/59 x 118000 = 48000

Answer: D) 5 minutes Explanation: Let the total capacity of tank be 90 liters.Capacity of tank filled in 1 minute by K = 3 liters.Capacity of tank filled in 1 minute by L = 15 liters.Therefore, capacity of the tank filled by both K and L in 1 minute = 18 liters.Hence, time taken by both the pipes to overflow the tank = 90/18 = 5 minutes.

Answer: C) 4 Explanation: Let the number of boys in the group originally be x.Total weight of the boys = 30xAfter the boy weighing 35 kg joins the group, total weight of boys = 30x + 35So 30x + 35 + 31(x + 1) = > x = 4.

Answer: B) 15 Explanation: Given when she sells at Rs. 160 for 20 articles, she get 40% loss.   Then, to get 20% profit selling at Rs. 240 for let 'P' articles   => 1602060=240p120   => 120 x 160 x P = 20 x 70 x 240   => P =  15 articles.

Answer: A) 48 Explanation: 3X + 4y = 240by substitute through options 48 is correct

Answer: A) Mercury Explanation:

Answer: B) Video & Graphics Explanation: VRAM or (video RAM), reference to any type of random access memory (RAM) is a dual-ported variant of dynamic RAM (DRAM) used to store the framebuffer in graphics adapters.