Answer: 11
Step-by-step explanation:
We know that mean of a number of observations is given by :-
\(\text{Mean}=\frac{\text{Sum of all observations}}{\text{Number of observations}}\\\\\Rightarrow\ \text{Sum of all observations}=\text{Mean*Number of observations}\)
Given: The mean weight of 8 backpacks = 14 pounds
\(\Rightarrow\ \text{Sum of weight of 8 backpacks}=14\times8=112\)
The mean weight of different 12 backpacks =9 pounds
\(\Rightarrow\ \text{Sum of weight of 12 backpacks}=12\times9=108\)
Now, Total sum of all observations = 112+108=220 pounds
Now, the mean weight of the 20 backpacks is given by :-
\(\text{Mean}=\frac{220}{20}=11\)
