The average of 30 numbers is 15. The average of the first 18 numbers is 10 and that of the next 11 numbers is 20. The last number is

If the students of a class can be grouped exactly into 6 or 8 or 10, then the minimum number of students in the class must be. 

If the product of four consecutive natural numbers increased by a natural number p, is a perfect square; then the value of p is: 

Direction: A shopkeeper has some kg. rice of same price. He sold 150 kg. rice at 25 Rs. per kg. and earned a profit of 25%, another 180 kg. rice is sold at a profit of 20% and rest are sold at a loss of 10%. If the shopkeeper earns Rs. 1230 profit on all the rice that he has sold then answers the following question:

If the shopkeeper earns 10% profit instead of 10% loss on the rest rice then find the difference between the old and new profit. 

Find the distance between the point (-6, 7) and the point (-1, -5).

In what time will the annual simple interest rate at $$ {6{1\over4}{\%}}$$ , 72 rupees becomes 81 rupees?

A boat can row 15 km per hour downstream and 9 km per hour upstream. The speed (in km/hour) of the boat in still water is:

In a factory, the production of cycles rose to 48,400 from 40,000 in 2 years. The rate of growth per annum is?