Something my top set Year 9 class struggled with when I presented it to them the other day. Hopefully this should fix it.
Backwards Mean Questions
Learning Objective: To be able to work backwards in problems when you are given the mean and have to work out other values.
This powerpoint file shows you how to work out the following problems:
Example 1 (“Missing Value”):
Jessica goes fishing. She catches 5 fish.
Their mean weight is 1.6 kg.
The weights of the first 4 fish (in kg) are:
1.5, 1.2, 0.9, 1.9
What is the weight of the fifth fish?
Example 2 (“New Mean”):
Mohibullah is taking some exams.
After his first 4 exams, his mean score is 79%.
In his fifth exam, he scores 64%.
What is his new mean score?