Answer :

Given that, first term of the first AP, a = 8 and that of second AP, A = - 30

and common difference of the first AP, d = 20 and that of second AP, D = 8

Given that

Sum of first n terms of first AP = Sum of first 2n terms of second AP

2a + (n - 1)d = 2[2 A + (2n - 1)D]

16 + (n - 1)20 = 2[2 × -30 + (2n - 1)8]

16 + 20n - 20 = 2[-60 + 16n - 8]

8 + 10n - 10 = -60 + 16n - 8

10n - 2 = 16n - 68

6n = 66

n = 11

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