The average weight of 17 students of a class is 56 kg. 3 new students whose weights are 57, 62 and 68 kg, respectively, join the class. Find the new average weight of the students of the class.

The average weight of 17 students of a class is 56 kg.

total weight of 17 students of a class = $$56\times17$$ = 952

3 new students whose weights are 57, 62 and 68 kg, respectively, join the class.

New average weight of the students of the class = $$\frac{total\ weight\ of\ 17\ students+sum\ of\ the\ weight\ of\ new\ students}{total\ number\ of\ students}$$

= $$\frac{952+57+62+68}{17+3}$$

= $$\frac{1139}{20}$$

= 56.95 kg