By reducing the circumference of a circle by 50 percent, by what percentage will its area decrease?

A cylindrical well of depth 21 m with internal radius of 13 m is dug up. The mud, so detained, is spread evenly to form a platform of dimension 52 × 13.2. What is the height of the platform?

The difference between simple interest and compound on Rs. 1200 for one year at 10% per annum reckoned half-yearly is:

Two pipes of length 36 metre and 40 metre are to be cut into equal pieces without leaving any extra length of pipe. Find the number of such pieces if pipes are to be cut of maximum length.

Directions: Each of the questions consists of a question followed by three statements. You have to study the questions and the statements and decide which of the statements(s) is/are necessary to answer the question. 

What is the population of State ‘A’?
 I. After increasing the population of State A by 15% it becomes 1.61 lakhs
 II. Ratio of population of State A to that of State B is 7 : 8 respectively
 III. Population of State B is 1.6 lakhs

‘A’ alone can complete a work in 6 days and “B” can complete this work alone in 8 days. They can complete this work in 3 days with the help of C. If they are paid Rs. 6400 for this work, then find the share of C.

Find out value of Cosec $$\left(-{5π\over3} \right)$$?

A discount of 20% in the price of rice enables X to buy 5 kg more rice for ₹100. What is the reduced price of rice per kg?