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 :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Champ Quiz | Arithmetic Progression34 mins
Champ Quiz | Arithmetic Progression30 mins
Smart Revision | Arithmetic Progression47 mins
Quiz | Arithmetic Progression44 mins
Smart Revision | General Term of an A.P44 mins
Lets Check Your Knowledge in A.P.49 mins
Master Arithmetic Progression36 mins
Quiz on Arithmetic Progression Quiz32 mins
Get to Know About Geometric Progression41 mins
NCERT | Solving Questions on Introduction of A.P42 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses