Find the average of first $25$ multiples of $5 .$
$65$
$60$
$75$
$80$
Sum of first $25$ multiples of $5=5(1+2+3 \ldots .25)$
$=5 \times \frac{25 \times 26}{2}=1625 \Rightarrow$ Average $=\frac{1625}{25}=65$
The daily earnings of a taxi driver during a week are: $Rs.0\,, Rs.65\,, Rs.70\,, Rs.52.50\,, Rs.63\,, Rs.73\,$ and $Rs.68$ What is his average daily earning for the week? (in $Rs.$)
The average speed of a train in the onward journey is $25\, \%$ less than that of the return journey, The train halts for one hour on reaching the destination. The total time taken for the complete to and fro journey is $17\, hours,$ covering a distance of $800 \,km$. The speed of the train in the onward journey is (in $km/h$)
The average marks of a student in four subjects is $75 .$ If the student obtained $80$ marks in the $5^{\text {th }}$ subject then the new average is?
Three year ago, the average age of a family of five members was $27 \,year.$ The present average age is also $27 \,year$ after the inclusion of a child into the family. Find the age of the child in $year$ ?
Out of nine persons$, 8$ persons spent $Rs.\, 30$ each for their meals. The ninth one spent $Rs.\, 20$ more than the average expenditure of all the nine. The total money spent by all of them was (in $Rs.\,$)
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