In a class there are 30 girls and 15 boys and total average weight of class is 47$frac{7}{{15}}$ kg. Total average weight of boys is 58 kg. Find the approximate average weight of girls ?

Total weight of students = $47frac{7}{{15}}left( {15 + 30} ight)$

= 2136 kg

Total weight of boys = 15× 58 = 870 kg

Average weight of girls = $left( {frac{{2136 - 870}}{{30}}} ight){ m{kg}} = 42.2{ m{kg}}$

≃ 42 kg