Average age of $5$ boys is $16$ $year$ of which that of $4$ boys is $16\, year\, 3\, months.$ The age of the $5^{th}$ boy is

The average earning of a mechanic for the first four days of a week is $Rs.\,18$ and for the last four days is $Rs.\,22.$ If he earns $Rs.\, 20$ on the fourth day, his average earning for the whole week is (in $Rs.$)

The average marks of $40$ students in an examination was $25 .$ It was later found that the marks of one student had been wrongly entered as $73$ instead of $37.$ What is the value of correct average

The average weight of a class of $24$ students is $35 \,kg$. If the weight of the teacher is included the average rises by $400\, g.$ The weight of the teacher is (in $kg$)

Find the average of first $25$ multiples of $5 .$

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?