The speed of a  boat in still water is 20 kmph and the rate of current is 4 kmph. The distance travelled by the boat downstream in 30 minute is

The difference between two whole numbers is 110 and the numbers are in ratio 2 : 7. Find the sum of the two numbers.

If a = 7, b = 5 and c = 3, then the value of $$a^2+b^2+c^2-ab-bc-ca$$ is 

The average age of 32 boys of a class is equal to 15 years. When the age of the class teacher is included the average becomes 16 years. Find the age of the class teacher. 

The diagonal of a square is equal to the side of an equilateral triangle. If the area of the square is $$ {18\sqrt{3}}$$ sq.cm. What is the area (in cm²) of the equilateral triangle ?

A radio is sold for Rs.900 at 10% profit. If it had been sold for Rs 890, what would have been the actual profit or loss?

Train A takes 1 hour more than train B to travel a distance of 720 km. Due to engine trouble speed of train B falls by one third, so it takes 3 hours more than Train A to complete the same journey. What is the speed of Train A (in km/hr)?

A can do a piece of work in 24 day, B in 32 days and C in 64 days. All begin to do it together, but A leaves after 6 days and B leaves 6 days before the completion of the work. How many days did the work last?