The ages of Shyam and Mohan are in the ratio of 11: 13 respectively after 7 years the ratio of their ages will be 20: 23. What is the difference in years between their ages?

$$ {a^2-b^2-2bc-c^2}\over{a^2+b^2+2ab-c^2}$$ is equal to

If the cost of 10 books is ₹250, then find the cost of 15 books.

Directions: The bar graph given below shows the production (in ' 000 tones) of rice of a country for the year 2007 to 2011. Study the graph carefully and answer the question given below it.

What is the percentage increase in the production of rice in the year 2008 in comparison to the year 2007? 

The average of 5 consecutive natural numbers is M. If the next three natural numbers are also included, how much more than M will the average of these 8 numbers be? 

Directions:  Study the bar-graph given below & answer the questions.
Pie-chart given below shows the percentage distribution of total no. of boys in six different Schools.
Total Boys in all schools together = 6400

If ratio of girls to total students in school E is 3 : 5. Then find difference of boys in school D to girls in school E?

Find the value of given equations

$$\left({216\over1} \right) ^{-{2\over3}}÷\left({27\over1} \right) ^{-{4\over3}}=? $$

The value of $$ cos {20^o} cos {40^o}cos {60^o}cos {80^o}$$ is: