Question

In an AP , if 1 = 1, = 20 = 399 then n
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Answer 1

Answer:

We know that Sn=2n[2a+(n−1)d]

⇒Sn=2n[a+a+(n−1)d]

⇒399=2n[a+an]            [an= last term]

⇒399=2n[1+20]

⇒n=21399×2=38

Answer 2

Answer:

Step-by-step explanation:

every number comes in 2 ki table is even