(1) Find the sum of the first 25 terms of each of the arithmetic sequences
below.
1) 11, 22, 33, ... ii) 12, 23, 34, ... iii) 21, 32, 43, ...
iv) 19, 28, 37, v) 1, 6, 11, ...
Answers
Answer:
3,575, 3,600, 3,825, 3,775, 1525
Step-by-step explanation:
1. a=11, d=22-11=11
sum of n terms is n/2(2a+(n-1)d)
sum of 25 terms = 25/2 (2*11+(25-1)11)
= 25/2(22+264)
= 25/2 * 286
= 3,575
2. a=12, d= 23-12= 11
sum of 25 terms = 25/2 (2*12+(25-1)11)
= 25/2 (24+264)
= 25/2 *288
= 3,600
3. a= 21, d= 32-21= 11
sum of 25 terms= 25/2 (2*21+(25-1)11)
= 25/2 (42 + 264)
= 25/2 * 306
= 3,825
4. a= 19, d= 28-19= 11
sum of first 25 terms= 25/2(2*19+(25-1)11)
= 25/2 (38+264)
= 25/2 (302)
= 3,775
5. a= 1 , d=6-1= 5
sum of first 25 terms= 25/2(2*1+(25-1)5)
= 25/2 (2+120)
= 25/2 (122)
= 1,525
hope it helped
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