The average weight of 18 boys in a group is 35 kg.If four new boys of weights 20 kg, 22 kg 26 kg and 28 kg are added to the group, then what is the average weight of the newly formed group?

Average formula = $$\frac{sum\ of\ weight\ of\ all\ boys}{total\ number\ of\ boys}$$

So,the average weight of 18 boys is 35 here,

from the above formula we get the total weight = 35$$\times$$18$$ $$ = 630.

When  four new boys joined the group of weight 20,22,26,28, now total weight will become = 630 + 20 + 22 + 26 + 28 = 726.

Now total number of boys increased to 22, hence average weight of new group = $$\frac{726}{22}$$ = 33.