Question

in a class after 20 girls and 15 boys the average weight of the class is 42 kg the average weight of the boys is 41.5 kg what is the average weight of the girls ​

Answer 1

Answer:

${\underline{\boxed{\bold{Average\:weight\:of\:girls=42.375\:kg}}}}$

Step-by-step explanation:

$\begin{gathered}\bf{Given-}\begin{cases}\sf{Average\:weight\:of\:class=42\:kg}\\\sf{Number\:of\:Boys=15\: and \: girls=15}\\\sf{Average\:weight\:of\:boys=41.5\:kg}\\\sf{Average\:weight\:of\:girls=?}\end{cases}\end{gathered}$

${\boxed{\bold{Average\:weight=\frac{Total\:weight}{Total \:number}}}}</p><p>$

$→\tt Average\:weight =\dfrac{Total\:weight\:of\: boys+Total\:weight \:of\: girls}{Total\:number}$

$→\tt 42 = \dfrac{(Number\times Av.weight)+(Number\times Av.age)}{20+15}</p><p>$

$→\tt 42 =\dfrac{(15 \times 41.5 + )+(20 \times N )} {35}</p><p>$

$→\tt 42 \times 35 = 622.5 + 20N42×35=622.5+20N$

$→\tt 1470 = 622.5 + 20N1470=622.5+20N$

$→\tt 20N = 1470 - 622.520N=1470−622.5$

$→\tt 20N = 847.520N=847.5$

$\tt \: \: \: *Dividing\:both\:terms\:by \:$

$→\tt N = 42.375\:kgN=42.375kg$

${\underline{\therefore{\bold{Average\:weight\:of\:girls=42.375\:kg}}}}$