The average marks obtained in a class of 50 students is 70%. The average of first 25 is 60% and that of 24 is 80%. What is the marks obtained by the last student?

If X is 20% less than Y, then find the value of $${Y-X\over Y}$$ and $${X\over X-Y }$$

The difference between the value of the number increased by 20 % and the value of the number decreased by 25 % is 36. Find the number. 

P is 20 percent more than Q and Q is 30 percent less than R. If P is 420, then What is the value of R?

A student got 30% marks in an examination and failed because he got 12 marks less. Another student got 40% marks in the same examination and got 18 marks more than the minimum passing marks. Must have marks to pass

What percentage of the whole week does Ajay spend in office, if his office hours are 9 am to 5 pm from Monday to Friday? 

In an examination, 93 % of students passed and 259 failed. The total number of students appearing at the examination was: 

By reducing the circumference of a circle by 50 percent, by what percentage will its area decrease?