Question

1.. if the first term of an A.P. is ─ 7 and the common difference is 5, its 18th term is :

2. The sum of the first 20 terms of the A.P. 1, 4, 7, 10, ……….. is :

Answer 1

Answer:

1. a+17d=-7+17×5= 78

2.Sn= n/2(2n-1)d

=20/2{2×20-1}3

10×38×3

1140 is the answer

Answer 2

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