Which of the two numbers should be reduced in the ratio of 15:19 so that the ratio becomes 3: 4?

Simplify the following

  $${\sqrt { 10+{\sqrt { 25+ {\sqrt { 108 +\sqrt { 154+ \sqrt { 225} \ } \ } \ }} \ } } \ }\over \sqrt { 16+ 19.25×4^2} $$

The area enclosed between the circumferences of two concentric circles is 45π square cm and their radii are in the ratio of 3:2. What is the area off the outer circle?

A unique circle can always be drawn through x number of given non-collinear points, then X must be 

Rahul divides some money among his three sons A, B and C. The ratio of amount received by A and C together to the amount received by B is 5:2. C received 150% of the amount received by A. If the amount received by C is Rs. 1500. Find the sum of amount received by A and B together.

If the clock is at 3:17, what time will be seen in the mirror?

A shopkeeper list the price of an article as ₹ 500. But he gives a certain discount which allows the buyer to pay ₹ 500 for the article including 10% sales tax. The rate of discount is 

A boat goes 15 km in an hour in still water, and takes thrice the time to cover the same distance upstream. The speed of the current (in km / hr) is –