Instructions

For the following questions answer them individually

Question 21

If the difference between the yearly compound interest for 2 years and simple interest for 3 years on a certain amount at 10% per annum is Rs. 1080, then that amount ( in Rs.) is

Question 22

A person borrowed some money for simple interest and the interest paid ti $$\frac{4}{9}th$$ of the principal. If the magnitudes of the interest rate and the time period are equal, then the rate of interest per annum is

Question 23

A person borrowed a sum for simple interest at a certain rate for a period of 3 years. If he has taken it for 2% higher rate, he would have to pay Rs. 720 more. Then the sum (in Rs.) borrowed by him is

Question 24

Sunil borrowed Rs. 25,000 from a money lender at 20% compound interest per annum. At the end of each year he repaid Rs. 5,000. The amount he still owes to the lender after paying three such instalments is (in Rs.).

Question 25

The number of times the number-key buttons of a typewriter have to be pressed in order to type the first 300 natural number is

Question 26

A hollow cylinder with diameter 6 cm is partially filled with water. A sphere of 3 cm diameter is gently dropped into the cylinder. If it is immersed in water, then the water in the cylinder raises to a further height of

Question 27

A hollow iron roller of length 63 cm and having girth 440 cm has a thickness of 4 cm. The volume (in cubic cms) of metal used for making it, is

Question 28

A solid cone of height 9 cm with base diameter 18 cm is cut out from a wooden solid sphere of radius 9 cm. The percentage of wood that is wasted in this process is

Question 29

Two pipes can separately fill a tank in 20 hrs and 30 hrs respectively. Both these pipes are opened simultaneously and after the tank is $$\ \frac{1}{3}$$rd full, a leak develops in the tank through which $$\frac{1}{3}$$rd of water supplied thereafter by both pipes gets leaked out. The total time (in hours) taken to fill the tank is

Question 30

A pipe can fill a cistern in 12 minutes while a second pipe fills it in 15 minutes. But a third pipe can empty that completely filled cistern 16 minutes. The first two pipes are kept open for 5 minutes initially and then the third one is also opened. Then the further time (in minutes) taken to empty that cistern is