The first and last term of an ap are 5 and 45 repectively. If the sum of all its term is 400. Find the common difference?
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Answer:
8/3
Step-by-step explanation:
Let the first term be a = 5 and the last term(l) = 45
an=last term (l) = a+(n-1)d where 'a' is the first term and d is the common difference.
45 =5+(n-1)d ⇒ (n-1)d =40
also given that sum of 'n terms = 400
⇒ Sn =(n/2)[a+l]
400 = n/2[5+45]
50n =800 ⇒ n=800/50 =16
n= 16 using this 'n' value in (n-1)d= 40 , we have 15d =40
⇒d =40/15 =8/3
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