The sequence is
44.4,49.2,56.4,61.2,68.4,73.2 .......
There is a total of 99terms.
The ans is 33442.8
How to add them up?(Please show the step)
sum of the sequence?
2014-08-04 5:06 pm
回答 (2)
2014-08-04 6:09 pm
✔ 最佳答案
If you look at it closely, you can see that the added increment alternates between 4.8 and 7.2 with an average of 6. Hence value 3 = value 1 + 2 x 6 = 44.4 + 12 = 56.4 and so on for every other odd numbered term. Accordingly, value 99 = value 1 + 98 x 6 = 44.4 + 588 = 632.4
You can get the desired answer by using the arithmetic series formula and subtracting 49 times 1.2 (the difference between 4.8 and 6
((44.4 + 632.4) x 49.5) - 49 x 1.2 = 33442.8
2014-08-04 5:39 pm
s_1=44.4
s_2=49.2
s_3=12+s_1
s_4=12+s_2
s_n=12+s_(n-2)
s_2=49.2
s_3=12+s_1
s_4=12+s_2
s_n=12+s_(n-2)
收錄日期: 2021-04-20 15:13:47
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