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↧↧↧ Detailed Video Solution to the Problem ↧↧↧



Let \(s_1\) be the sum of the first n terms of the arithmetic sequence 8, 12, . . . and let \(s_2\) be the sum of the first n terms of the arithmetic sequence 17, 19 . . .

First series is given by 8, 12,...
First term, a = 8
Common difference, d = 12 - 8 = 4
Number of terms = n
Sum of Terms, \(s_1\) = \(\frac{n}{2}\) * (2a + (n-1)*d) = \(\frac{n}{2}\) * ( 2*8 + (n-1)*4) = \(\frac{n}{2}\) * (16 + 4n - 4)
= \(\frac{n}{2}\) * ( 12 + 4n)

Second series is given by 17, 19,...
First term, a = 17
Common difference, d = 19 - 17 = 2
Number of terms = n
Sum of Terms, \(s_2\) = \(\frac{n}{2}\) * (2a + (n-1)*d) = \(\frac{n}{2}\) * ( 2*17 + (n-1)*2) = \(\frac{n}{2}\) * (34 + 2n - 2)
= \(\frac{n}{2}\) * (32 + 2n)

\(s_1\) = \(s_2\)
=> \(\frac{n}{2}\) * ( 12 + 4n ) = \(\frac{n}{2}\) * ( 32 + 2n )
=> 12 + 4n = 32 + 2n
=> 2n = 20
=> n = 10
=> One value of n

So, Answer will be B
Hope it helps!

Watch the following video to MASTER Sequences

­
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