The average salary, per head, of all the workers of an institution is 60. The average salary of 12 officers is 400; the average salary, per head, of the rest is 56. The total number of workers in the institution is -

(sec A + tan A – 1) (sec A – tan A+1) =?

If $$ {x+{9\over x}=6}$$  then find the value of $$ {x^{2}+{1\over x^{3}}}$$

A work can be completed by 20 men in 50 days. 30 more men join them after 10 days of work. How many days will be saved in completion of the work?

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?

Train A moving at speed 72 kmph crosses train B moving at 3/4th speed of train A in the same direction in 1 min and 26 seconds. The length of train A is 25/18th of the length of train B. What is the difference between the lengths of two trains?

If a seller bought an item for Rs. 900 and determined the mark price in such a way that after giving 10 percent discount, he would get a profit of 20 percent, what would be the mark price?

Read the following graph carefully and answer the related questions-

Total number of students (in thousands) participating in comitative exam in various cities.

What is the ratio of number of students appearing for competitive exam from city C and D together to those appearing from A, D and E together?