Find the value of $$ {1\over{2×5}}+{1\over {5×8}}+{1\over {8 × 11}}+......{1\over {23 × 26}}=?$$

The average score obtained by Sandeep in 12 Tests is 25. Rumella has an average of 23 marks so far, but has competed in only 8 Tests. What average will Rumela have to earn in the remaining 4 Tests to be equal to Raghuveer's average?

A man can row at a speed of $$4{1\over 2}$$km/hr in still water. If he takes 2 times as long to row a distance upstream as to row the same distance downstream, then the speed of stream (in km/hr) is : 

A circular ground of radius  7 m is surrounded by a path of width 3.5 m. Find the area of path.

A trader sells two items at the rate of Rs 400 each. If he gains 15% on one and losses 15% on other, then what is the value (in Rs) of loss?

If $${4x^2={15^2-9^2}}$$ then the value of x is

Some persons can do a piece of work in 12 days. Two times the number of such persons will do half of the work in