If Sonu is driving a car with a speed of 20 m/s, then in what time will Sonu cover a distance of 936 km?

A can finish a piece work in 18 days and B can do the same work in half of the time taken by A. Then working together what part of the same work they can finish a day?

In a school there are total 414 students. The ratio of boys and girls is 5 : 4. If 46 more boys gets admitted into the school, then what will be the new ratio of boys and girls?

If the sum of the interior angles of a regular polygon be 1080 °, the number of sides of the polygon is 

A person borrows 5,000 for 2 years at 4 % per annum simple interest. He immediately lends it to another person at $$6{1\over 4}\%  $$ per annum simple interest for 2 years. His gain in this transaction is 

Area of the smallest square that can circular ring enclosed Ween of area 616 cm² is 

$$ \sqrt{.081×.484\over0.0064×6.25}=?$$

What should come at place of question mark (?) in the following number series?

15 20 50 165 680 ?