Let S be the sum,
S = 2 + 4 + 6 + ... + 2 (n - 2) + 2 (n - 1) + 2n
Reverse the order of terms:
S = 2n + 2 (n - 1) + 2 (n - 2) + ... + 6 + 4 + 2
Add up terms in the same positions, so that twice the sum is
2S = (2n + 2) + (2n + 2) + (2n + 2) + ... + (2n + 2)
or
2S = n (2n + 2)
Divide both sides by 2 to solve for S :
S = n (n + 1)
Answer: the one that ends with 30. D the fourth one
Step-by-step explanation:
First, write out all the values:
40,41,41,45,48,48,49,49,49,50
Then to find the mean, you add all the values and divide by the number of values (there are 10 values)
(40+41+41+45+48+48+49+49+49+50)/10
460/10
=46
Hope this helps
Answer:
8 hours
Step-by-step explanation:
6x+20=68
subtract 20 from both sides
6x=48
divide 6 both sides
x=8
