Answer:
The variance is 
Step-by-step explanation:
From the question we are told that
The sample size is n = 21
The sum of squares is 
Generally the variance is mathematically represented as

substituting values


The answer is 28
30 minutes is half of an hour so you have to divide 7 by 2 which is 3.5 and then multiply 3.5 by 8 to get 28
Answer:
4a^2 - 15b + 9b^2
Step by step explanation:
Answer: 2 1/2
Step-by-step explanation: Divide using long division. The whole number portion will be the number of times the denominator of the original fraction divides evenly into the numerator of the original fraction, and the fraction portion of the mixed number will be the remainder of the original fraction division over the denominator of the original fraction. Hope this helps!! PLZ mark me!!!