Question

in a class 20 girlsand 15 boys the average weight of class is 42 kg the average weught of boy is 41.5 kg what is the average weight of girl​

Answer 1

Answer:

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

Step-by-step explanation:

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

Let the av.weight of girls be N kg.

$\tt Formula\:used:-$

${\boxed{\bold{Average\:weight=\frac{Total\:weight}{Total \:number}}}}$

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

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

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

→$\tt 42 \times 35 = 622.5 + 20N$

→$\tt 1470 = 622.5 + 20N$

→$\tt 20N = 1470 - 622.5$

→$\tt 20N = 847.5$

$\tt \: \: \: *Dividing\:both\:terms\:by \: 20$

→$\tt N = 42.375\:kg$

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

Answer 2

$\huge{\underline{\underline{\red{\mathfrak{AnSwEr :}}}}}$

$\small{\underline{\blue{\sf{Given :}}}}$

• Number of Boys = 15
• Number of Girls = 20
• Average weight of boys = 41.5 kg
• Average Weight of Class = 42 kg

$\rule{200}{1}$

$\small{\underline{\green{\sf{Solution :}}}}$

$\large \star {\boxed{\sf{Average \: Weight \: = \: \dfrac{Total \: Weight}{Number \: of \: Students}}}} \\ \\ \small \implies {\sf{Average \: = \: \dfrac{(Avg.Wt \: of \: Boys) (No. \: of \: Boys) \: + \: (Avg.Wt \: of Girls)(No. \: of \: Girls)}{Total \: Students}}} \\ \\ \implies {\sf{42 \: = \: \dfrac{(15 \: \times \: 41.5) \: + \: (20 \: \times \: x)}{15 \: + \: 20}}} \\ \\ \implies {\sf{42 \: = \: \dfrac{622.5 \: + \: 20x}{35}}} \\ \\ \implies {\sf{42 \: \times 35 \: = \: 622.5 \: + \: 20x}} \\ \\ \implies {\sf{1470 \: = \: 622.5 \: + \: 20x}} \\ \\ \implies {\sf{20x \: = \: 1470 \: - \: 622.5}} \\ \\ \implies {\sf{20x \: = \: 847.5}} \\ \\ \implies {\sf{x \: = \: \dfrac{847.5}{20}}} \\ \\ \implies {\sf{x \: = \: 42.375}}$

∴ Average Weight of girls is 42.375 kg