sum of 15 terms of an AP is 600, and the common difference is 5 .find the first term
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Given n=15, S15=600, d=5
We know that
Sn=n2[2a+(n−1)d]
⇒S15=152[2a+(15−1)5]=152[2a+(14)5]=15(a+35)
⇒600=15(a+35)⇒60015=a+35⇒40=a+35⇒a=
40−35=5
Hence first term=5
Given n=15, S15=600, d=5
We know that
Sn=n2[2a+(n−1)d]
⇒S15=152[2a+(15−1)5]=152[2a+(14)5]=15(a+35)
⇒600=15(a+35)⇒60015=a+35⇒40=a+35⇒a=
40−35=5
Hence first term=5
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