The average marks of $40$ students in an English exam is $72 .$ Later it is found that three marks $64 , 62$ and $84$ were wrongly entered as $68,65$ and $73.$ The average after mistakes were rectified is

The average price of $80$ computers in an electronic shop is $Rs.\, 30,000 .$ If the highest and lowest price computers are sold out then the average price of the remaining $78$ computers is $Rs.\, 29,500 .$ The cost of the highest price computer is $Rs.\, 80,000 .$ The cost of lowest price computer is in $Rs.$ 

Five years ago, the average age of $P$ and $Q$ was $15 \,year.$ Now, average age of $P , Q$ and $R$ is $20 \,year.$ What whould be the age of $R$ after $10$ $year$ in $year$ ?

Average weight of $25$ persons is increased by $1 \,kg ,$ when one man weighing $60\, kg$ is replaced by a new person. Weight of new person is? (in $kg$)

The mean of the marks obtained by $100$ students is $60 .$ If the marks obtained by one of the students was incorrectly calculated as $75$ whereas the actual marks obtained by him were $65,$ what is the correct mean of the marks obtained by the students?

The average marks of a student obtained in Physics, Chemistry and Biology is $70.$ If the student obtained $90\, marks$ in Mathematics, then the new average is