The 4th term of an AP is 11. the sum of the 5th and 7th terms of this AP is 34. Find its common difference.
Here, a4=11⇒a+3d=11...(1)
Also, a5+a7=34⇒a+4d+a+6d=34⇒a+5d=17...(2)
Subtracting (1) from (2), 2d=17−11=6⇒d=3
The 5th term of an AP is 20 and the sum of its 7th and 11th terms is 64. the common difference of the AP is (a) 4 (b) 5 (c) 3 (d) 2