If ( 2x – y): ( 5x+3y)=3 : 8 then ( x² + y²) : ( x² – y²)=?

If a sum of money becomes 8 times in 9 years at compound interest annually, in how much time it will become 32 times?

Krishna bought a camera and paid 20 % less than its original price. He sold it at 40 % profit on the price he had paid. The percentage of profit earned by Krishna on the original price was 

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)?

If 0.5x + 0.7y=0.5 and 0.7x + 0.5y=0.7,then the value of x+y is

Directions : What will come in the place of the question mark (?) in the following number series?

2  4  11  37  ? 

In an examination, 50% of the students passed in Science and 75% passed in Social Science, while 20% students failed in both the subjects. If 270 students passed in both subjects, find the total number of students who appeared in the exam?

What is the average of the following numbers?
38, 92, 45, 25, 60