S=n/2(2a+(n-1)d). If d=5, n=13, S=585 find the value of a.

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Bandreid asked Sep 1, 2022

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S=n/2(2a+(n-1)d). If d=5, n=13, S=585 find the value of a.

Mathematics
high-school

Bandreid asked Sep 1, 2022

by Bandreid

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Answer:

Explanation:

Sum of 'n' terms formula is given by:-

s=n/2(2a+(n-1)d)

s=13/2[2xa+(13-1)5]

s=13/2(2xa+12x5)

s=13/2(2a+60)

585=13/2(2a+60)

585 x (2/13) = 2a + 60

90 = 2a + 60

90-60 = 2a

30 = 2a

a = 15

Lucas Eduardo answered Sep 6, 2022

by Lucas Eduardo

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