In an AP :
given a = 7, an = 35 find d and s13
d is the common difference
a is the first term = 7
a13 = 35
a13 = a + (13-1)d
35 = 7 + (12)(d)
28 = 12 d
d = 
The sum of the series is Sn = 
[2a + (n-1) d]
S13 = 
[2×7 + (13-1) 
]
= 
[42]
= 273
3
In an AP :
given a = 7, an = 35 find d and s13
d is the common difference
a is the first term = 7
a13 = 35
a13 = a + (13-1)d
35 = 7 + (12)(d)
28 = 12 d
d =
The sum of the series is Sn = [2a + (n-1) d]
S13 = [2×7 + (13-1) ]
= [42]
= 273