A) 36.5 kg
B) 35 kg
C) 36 kg
D) 35.6 kg
Correct Answer: C
Solution :
| Given that, |
| Number of boys\[({{n}_{1}})=15\] |
| Number of girls \[({{n}_{2}})=10\] |
| Average weight of boys and girls \[({{x}_{12}})=38.4\,\,kg\] |
| Average of boys \[({{\bar{x}}_{1}})=40\,\,kg\] |
| Let average of girls be \[{{x}_{2}}.\] |
| By formula, |
| \[s\,\,({{\bar{X}}_{12}})=\frac{{{n}_{1}}{{x}_{1}}+{{n}_{2}}{{x}_{2}}}{{{n}_{1}}+{{n}_{2}}}\] |
| \[\Rightarrow \] \[38.4=\frac{15\,\,(40)+10{{x}_{2}}}{15+10}\] |
| \[\Rightarrow \] \[10{{x}_{2}}=38.4\times 25-15\times 40\] |
| \[=960-600=360\] |
| \[={{x}_{2}}=36\,\,kg\] |
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