(ii) the sum of first 15 terms of an
a.p. is 750 and its first term is 15. find its 20th term.
Answers
Answered by
7
Given,
Sum of 15 terms = 750
Sn = n/2 * (A1 + An), where A1=first term, An = nth(15th) term
750 = 15/2 *(15 + A15)
50 = 1/2 *(15+A15)
100 = 15 + A15
A15 = 85
An = A1 + (n-1)*d
A15 = 15 + 14*d
85 = 15 + 14*d
70 = 14*d
d = 5
Hence,
A20 = A1 + (20-1)*d
A20 = 15 + 19*5 = 110
20th term of given A.P is '110'
Hope it helps.
Sum of 15 terms = 750
Sn = n/2 * (A1 + An), where A1=first term, An = nth(15th) term
750 = 15/2 *(15 + A15)
50 = 1/2 *(15+A15)
100 = 15 + A15
A15 = 85
An = A1 + (n-1)*d
A15 = 15 + 14*d
85 = 15 + 14*d
70 = 14*d
d = 5
Hence,
A20 = A1 + (20-1)*d
A20 = 15 + 19*5 = 110
20th term of given A.P is '110'
Hope it helps.
Answered by
5
Please find the attachment...
Hope it helps!!!
Attachments:
Similar questions