False because the factor tree for 61 is 1 and 61
Answer:

--- Variance
Step-by-step explanation:
Given

Solving (a): Calculate the mean.
The given data is a grouped data. So, first we calculate the class midpoint (x)
For 51 - 58.

For 59 - 66

For 67 - 74

For 75 - 82

For 83 - 90

So, the table becomes:

The mean is then calculated as:



-- approximated
Solving (b): The sample variance:
This is calculated as:

So, we have:


-- approximated
Answer 5.5
Explanation 125 + 125= 250
250 + 50=300
Is 2 125s and 1 50
Each 125 is 2.5
But in this case there is 2 125s
2.5+2.5=5
plus the other half = 5.5
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