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

Pipes  A and B are emptying pipes and can empty a tank in 6 hours and 16 hours, respectively. C is a filling a pipe. All the three pipes were opened together. They took 80 minutes to empty $$ {5\over 8}th$$ of the tank. Pipe C alone can fill the tank in:

How many perfect squares lie between 120 and 300? 

If x - y = 3, then what is the value of x³ - y³-9xy? 

If (x +y) = 6 and x² + y² = 20 then find the value of (x - y) ².

A man engaged a servant on the condition that he would pay him Rs. 90 and a turban after service of one year. he served only for nine months and received the turban and an amount of Rs. 65. The price of turban is: 

What is the volume of a cube whose side is 7.5 cm?

If the selling price of a product is multiplied by 2, the resulting profit is 6 times the original profit. What is the original profit percentage?