Find the standard deviation of the following data (rounded off to two decimal places). 5, 3, 4, 7 

Each side of a square is 6 cm. On which a pyramid has been built, its slant height is 4: 2 cm. Find the total surface of the pyramid?

From four corners of a square sheet of side 4 cm, four pieces, each in the shape of arc of a circle with radius 2 cm, are cut out. The area of the remaining portion is:

Average present ages of A, B and C is 25 years. The ratio of the present ages of B and C is 4:5. After 6 years, the ratio will be B and C is 5:6, then what is the present age of A?

A can do a piece of work in 18 days and B in 36 days. If they work together for 9 days, then what percentage of work will be left?

What is the perimeter of a square inscribed in a circle of radius 5 cm?

The probabilities of solving a problem by three students A, B and C are  $$3\over 7$$, $$5\over 9$$ and $$1\over 5$$ respectively. The probability that problem will be solved is:

In the following diagram, three different products (in thousands) produced by a company in 5 years are given and after studying them carefully, answer the following questions.

Three products produced by a company in different years (in thousands)

What is the average number of pan-drives produced by the company in all the years?