4) The banker's discount on a certain sum due 2 years hence is 11/10 of the true discount. The rate percent is

5) A man purchased a cow for Rs. 3000 and sold it the same day for Rs. 3600, allowing the buyer a credit of 2 years.

6) The simple interest and the true discount on a certain sum for a given time and at a given rate are Rs. 85 and Rs. 80 respectively. The sum is:

7) The angle of elevation of the sum, when the length of the shadow of a tree 3 times the height of the tree, is

8) For which of the following disciplines is Nobel Prize awarded?