A boat goes from A to B in upstream and come back from B to A downstream taking a total time of 3.5 hours. If the speed of boat in still water is 7 km/hr and the speed of stream is 5 km/hr. Find the distance between A and B. 

Simplify the following equation
$$ {\sqrt{(1-sin^{2}θ) ÷{(1-cos^{2}θ)}}}$$

Aman and Ajay can build a wall in 9 days and 12 days respectively. In how many days can they finish the work if they work together?

Simple interest on an amount is Rs. 24 and true discount on the same is Rs. 20. The principal amount is

If the profit on selling an article for Rs. 579 is the same as the loss on selling it for Rs. 337, then find the profit percent if its selling price is Rs. 687.

The average of x numbers is 48. If of the numbers are increased by 51 each and remaining are decreased by 71 each, then what is the new average?

$$ {4\over 5}×[{1\over 2}\ of\ 25]+12÷{3\over 4}-32=?$$

Four pipes P, Q, R and S can fill a cistern in 25, 20, 50 and 40 hours respectively. The pipe Q was opened at 7 pm, P at 9 pm, S at 10 pm and R at 11 pm. When will the cistern be full?