Quantitative Aptitude - Arithmetic Ability Questions

What approximate value should come in place of the question mark (?) in the following questions? (You are not expected to calculate the exact value.)

21.003 × 39.998 –209.91 = 126× ?

What is (x-y)3+y-23+z-x33x-yy-zz-x =?

A dealer marks a washing machine for Rs. 7500, and allows a discount of 6% on it. Find the selling price

The marked price of an article is Rs. 5000. But due to a special festive offer a certain percent of discount is declared. Mr. X availed this oppurtunity and bought the article at reduced price. He then sold it at Rs. 5000 and thereby made a profit of 11 1/9%. The percentage of discount allowed was?

A bookseller bought 500 text books for  20,000. He wanted to sell them at a profit so that he get 50 books free. At what profit percent should he sell them?

A, B and C invest in a business in the ratio 4 : 5 : 7. C is a sleeping partner, so his share of profits will be half of what it would have been if he were a working partner. If they make Rs 36,000 profit of which 25% is reinvested in the business, how much does B get (in Rs)?

Marked price of an item is Rs 200. On purchase of 1 item discount is 5%, on purchase of 2 items discount is 14%. Rajeshri buys 3 items, what is the effective discount? 

If one more cobbler is hired the output of a shoe making unit will increase from 50 pairs of shoes to 55 pairs per day, but then the shoe making unit will have to reduce the price of a pair of shoes from Rs 3200 to Rs 3000 per pair to sell the additional output, the marginal revenue product of the last cobbler is