An amount doubles itself in 5 years simple interest. What is the rate of interest per year?

if 120% of a is equal to 80% of b, then $${b+a}\over {b-a}$$ is equal to

A number when divided by 5 leaves a remainder 3. What is the remainder when the square of the same number is divided by 5 ? 

If u : v= 4 : 7 ,  v : w = 9 : 7 and u=72 then find the value of w.

If sin A=$${6\over 7}$$, then what is the value of sec A?

If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is: 

Directions : Study the following frequency polygon and answer the questions. Given a line graph showing the number of students passed in Higher Secondary Examination in a school over the years 2008 to 2013.

The increase in percentage of passed students from 2008 to 2011 approximately is 

The line graph shows the number of vacancies of accountants in a certain company. Study the diagram and answer the following questions.

What is the different between maximum and minimum vacancies?