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Answer:
d=4
Step-by-step explanation:
SUM OF 15 terms = 615
T5 = 53
T5 = a+(n-1)d
53 = a + 4d
4d = 53 - a
d = (53-a)/4
S15 = 15/2 (2a+14d) =615
15/2 [2a + 14×(53-a)/4 ]
=15/2 [ 2a +(53×14 - 14a )/4 ]
=15/2 [ (8a +742 - 14a ) /4]
615×8 = 15(-6a +742)
-6a+72=615×8/15 =41
-6a+72=42
-6a = - 72 + 42 = -30
a = 30/6= 5
a = 5
T5 = 5 + 4×d = 53
4d= 53 - 5 = 48
4d=48
d=4
Common difference is 4