Q. 1 J4.5( 10 Votes )

# Choose the correct alternative answer for each of the following sub questions.In an A.P. 1st term is 1 and the last term is 20. The sum of all terms is = 399 then n = . . .A. 42B. 38C. 21D. 19

Given, first term = 1

Last term = 20

Sum of n terms, Sn = 399

We need to find no. of terms n

Using Sum of n terms of an A.P. formula where n = no. of terms

Sn = sum of n terms

Now, on substituting given value in formula we get,   Rate this question :

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