Answer:
11
Step-by-step explanation:
Solution for this problem is in this picture.
Given sequence:
-2,-7,-12 ,..
Unknown;
Find the sum of the first 20 terms = ?
Solution:
The sequence is -2,-7,-12 ,..
To find he sum of n-terms of a sequence, we use the expression below;
Sₙ = 
where n is the number of terms = 20
a is the first term = -2
d is the common difference= -7 - (-)2 = -5
Now input the parameters and solve;
Sₙ = 
Sₙ = 10(-4 + -5(19)) = 10(-99) = -990
The sum of the first 20 terms of the sequence is -990
The mean is 4.93333 (3 is repeating)
Explanation
So mean is just the sum of the numbers divided by the number of terms
So we would solve this by adding up all terms as shown here
10.6 + 4 + 4 + 6 + 4 + 1 = 29.6 = sum
Then we will divide the sum by the number of terms which is 6 in this case to get our mean as shown here
29.6 / 6 = 4.9333
The mean is 4.9333 (3 is repeating)
1) the ones digit stays at 2 the tens increase by 1.