A mixture of 40 liters of milk and water contains 30% water. How much milk should be added to this mixture so that the new mixture contains 80% milk?

If 2x + 3y - 5z = 18 , 3x + 2y + z = 29 and x + y + 3z = 17 , then what is the value of xy + yz + zx ? 

Directions: The Bar Graph given here shows the population (in crores) of India in various census years. Observe the graph and answer the question based on it.  

In which census year, the percent increase in population is least as compared to that in the previous census year? 

A sum of Rs. 2000 amounts to Rs. 4000 in two years at compound interest. In how many years does the same amount becomes Rs. 8000. 

The length, width and height of a room are 10 meters, 8 meters and 6 meters respectively. What will be the largest bamboo length that can be kept in this room?

An item is sold at two successive gains of 30% and 20%. If the final selling price is Rs 31200, then what is the cost price (in Rs)?

A sells a bicycle to B at a profit of 20%. B sells it to C at a profit of 25%. If C pays Rs. 225/- for it, the cost price of the bicycle for A is: 

$$ sin^2 5° + sin^2 10°+sin^2 15°+.....sin^2 85°+sin^2 90°$$ is equal to