A person covers 9, km with a speed of 3 ,km / h , 25 ,km with a speed of 5, km / h and 30, km with a

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4.Average

medium

A person covers $9\, km$ with a speed of $3 \,km / h , 25 \,km$ with a speed of $5\, km / h$ and $30\, km$ with a speed of $10\, km / h$. Find out the average speed of person in $km / h$ ?

$5 \frac{9}{11}$

$11 \frac{5}{9}$

$9 \frac{5}{11}$

$5 \frac{5}{11}$

Solution

Here $a=9 km , b =25 km , c =30 km$

$P =3 km / hr Q =5 km / hr R =10 km / hr$

$\therefore$ Requried average speed

$=\frac{a+b+c}{\frac{a}{p}+\frac{b}{Q}+\frac{c}{R}}=\frac{9+25+30}{\frac{9}{3}+\frac{25}{5}+\frac{30}{10}}=\frac{64}{3+5+3}=\frac{64}{11}=5 \frac{9}{11} km / hr$

Hence average speed of a person $=5 \frac{9}{11} km / h$

Standard 13

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A person covers $9\, km$ with a speed of $3 \,km / h , 25 \,km$ with a speed of $5\, km / h$ and $30\, km$ with a speed of $10\, km / h$. Find out the average speed of person in $km / h$ ?

Solution

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