If the average of $6$ consecutive even numbers is $25,$ the difference between the largest and the smallest number is

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

Five years ago,the average age of $P$ and $Q$ was $15 \text{ years}$. Now,the average age of $P$,$Q$,and $R$ is $20 \text{ years}$. What will be the age of $R$ after $10 \text{ years}$?

$A$ person travelled from one place to another at an average speed of $40 \, km/h$ and back to the original place at an average speed of $50 \, km/h$. What is his average speed in $km/h$ during the entire trip?

The average age of three boys is $15$ years. If the ratio of their ages is $3:5:7$,what is the age of the oldest boy in years?

$A$ man spends on an average $Rs. 269.47$ for the first $7$ months and $Rs. 281.05$ for the next $5$ months. Find out his monthly salary if he saved $Rs. 308.46$ during the year. (in $Rs.$)