1
Question
The sum of 3rd and 11th terms of an AP is 34. Find the sum of its 13 terms.
Open in App
Solution
We know that
third term = a+2d-------a
and,
11th term = a+ 10d--------b
now ,equation a+b gives
2a+12d=34-----------given
now sum of 13 terms is
Sn=S13 = 13/2×[2a+12d]
S13=13/2×34 ---------[2a+12d=34]
therefore S13= 13 ×17= 221
answer=221
third term = a+2d-------a
and,
11th term = a+ 10d--------b
now ,equation a+b gives
2a+12d=34-----------given
now sum of 13 terms is
Sn=S13 = 13/2×[2a+12d]
S13=13/2×34 ---------[2a+12d=34]
therefore S13= 13 ×17= 221
answer=221
Suggest Corrections
2
Similar questions
View More
Join BYJU'S Learning Program
Explore more
Join BYJU'S Learning Program
