Answer: Donna is wrong. Mean weight is 7.1kg
Step-by-step explanation:
Calculate the mean for the bricks:
4 bricks have a mean weight of 5kg = 4 * 5
5 bricks have a mean weight of 9kg = 5 * 9
1 green brick is 6kg
= (4 * 5 ) + ( 5 * 9) + 6
= 71kg
Mean = 71 / (4 + 5 + 1)
= 7.1 kg
