Average of $a, b$ and $c$ is $11 ;$ average of $c, d$ and $e$ is $17 ;$ average of $e$ and $f$ is $22$ and average of $e$ and $c$ is $17 .$ Find out the average of $a, b,$ $c , d , e$ and $f ?$
$15 \frac{2}{3}$
$18 \frac{1}{2}$
$21 \frac{1}{3}$
$16 \frac{1}{2}$
The average age of $6$ members of a family is $20\, years.$ If the age of a servant is included, the average age increased by $25 \%$. What is the age (in $years$) of the servant ?
An aeroplane flies along the four sides of a square field at speeds of $200,400,600$ and $800\, km / hr$. The average speed of the plane in the flight around the field in $km / hr$ is:
The average speed of a cyclist who covers first, second and third km at $20,16$ and $12\, km / hr$ respectively ( in $km / hr )$ is
The mean weight of $150$ students in a class is $60 \,kg.$ The mean weight of boys is $70\, kg$ and that of girls is $55 \,kg$. What is the number of boys in the class?
The daily maximum temperature in Delhi, for $7$ consecutive days in $May \,1988 ,$ were $42.7^{\circ} C , 44.6^{\circ} C$, $42.0^{\circ} C , 39.1^{\circ} C , 43.0^{\circ} C , 42.5^{\circ} C$ and $38.5^{\circ} C$. Find out the average daily maximum temperature. (in $^{\circ} C$)