The first and last terms of an AP are 7 and 49 respectively. If sum of all terms is 420, find its common difference.
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Step-by-step explanation:
Therefore, the common difference of the given A.P. is 3.
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Answered by
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Answer:
Answer
a=7 l=49 Sn=420
Sn=
2
n
[a+l]
So 420×2=n[7+49]
n=15
l=a+(n−1)d
⇒ 49=7+14 d
⇒ 7=1+2 d ⇒ 2d=6
⇒ d=3
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