The average weight of $10$ parcels is $28.6\text{kg}$. The addition of a new parcel reduces the average weight by $0.6\text{kg}$. What is the weight (in kg) of the new parcel?

Method 1: Total Weight CalculationTotal weight of $10$ parcels:
$${\text{Total}}_{10}=10\times 28.6=286\text{kg}$$
When a new parcel is added, the total number of parcels becomes $11$, and the new average reduces by $0.6\text{kg}$:
$$\text{New Average}=28.6-0.6=28\text{kg}$$
Total weight of $11$ parcels:
$${\text{Total}}_{11}=11\times 28=308\text{kg}$$
Weight of the new parcel:
$$\text{Weight}=308-286=22\text{kg}$$
Method 2: Deviation Method
$$\text{Weight of new parcel}=\text{New Average}-(\text{Initial number of parcels}\times \text{Decrease in average})$$
$$\text{Weight}=28-(10\times 0.6)=28-6=22\text{kg}$$