Directions : What will come in the place of the question mark (?) in the following number series?

100 100   50  150  37.5 ?

The MRP of a article is 60% above its manufacturing cost. The article is sold through a retailer, who earns 19% profit on his purchase price. What is the approx. profit percentage for the manufacturer who sells his article to the retailer? The retailer gives 15% discount on MRP.

A shop - keeper sells a badminton racket whose marked price is ₹ 30, at a discount of 15 % and gives a shuttle cock costing ₹ 1.50 free with each racket. Even then he makes a profit of 20 %. His cost price, per racket is 

If 3 sin x + 5cosx = 5 then what is the value of (3cosx - 5sinx)

A shopkeeper marked the price of an article by 40% above cost price and gave discount of Rs. 224. On the final amount, he charged 10% tax. In the whole transaction, he earned Rs. 158.6. Find cost price of the article.

A vessel contains 60 litres of milk. 12 litres of milk taken out from it and replaced with water. Then again form mixture, 12 litres is taken out and replaced with water. The ratio of milk and water in the resultant mixture is :