3) The banker's discount of a certain sum of money is Rs. 72 and the true discount on the same sum for the same time is Rs. 60. The sum due is

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