Two pipes, D and E, can fill a cistern in 26 and 78 hours, respectively, while working alone. If the two pipes are opened together, the time taken to fill the cistern is:

If the height and the radius of the base of a cone are both doubled, the volume of the cone becomes _______ of its previous volume.

A man bought a chair for ₹580. At what price should he sell the chair so as to gain 25%?

Find the LCM of the fractions $${2\over 5}$$, $${3\over 7}$$ and $${4\over 9}$$

If A = 1300 and B = 1450, then B is approximately what percentage more than A?

Simplify the following expression.

 25-(4÷2)+11.5+9.5

Select the number that will come in place of the question mark (?) in the following mathematical statement.

$${5\over 9} \ of \ {11\over 14}\ 42\% \ of \ 540=?^2 -45 $$

A train running at the speed of $${140\over 9} $$  m/sec, crosses a pole in 27 sec. Find the length of the train.