The total marks obtained by a student in Physics,Chemistry and Mathematics together is $120$ more than the marks obtained by him in Chemistry. What is the average marks obtained by him in Physics and Mathematics together?

In a set of prime and composite numbers,the number of composite numbers is twice the number of prime numbers,and the average of all the numbers in the set is $9$. If the number of prime numbers and composite numbers are exchanged,then the average of the set of numbers increases by $2$. If,during the exchange of the numbers,the average of the prime numbers and composite numbers individually remained constant,then what was the ratio of the average of composite numbers to the average of prime numbers (initially)?

Out of seven given numbers,the average of the first four numbers is $4$ and that of the last four numbers is also $4$. If the average of all the seven numbers is $3,$ then the fourth number is?

Of the three numbers, the second is twice the first and thrice the third. If the average of the three numbers is $44$, then the largest number is

$30$ pens and $75$ pencils altogether were purchased for $Rs. \, 510$. If the average price of $75$ pencils was $Rs. \, 2$,then what was the average price of a pen? (in $Rs.$)

What is the average of the squares of the first $19$ natural numbers?