Total Price:

There are no items in this cart.
Continue Shopping

If Sn denotes the sum to n terms of the series 1<=n<=9

1+22+333+......+999+...... , then for n=>2

                    (9 times)


a). Sn-Sn-1=1\9(10n-n2+n)                           b).S

c). 9(Sn-Sn-1)=n(10n-1)                               d).S3= 356

4 years ago


Answers : (1)


Dear swapnil ,

there is a method of solving objective questions called solving by elimination. although we can try about solving for Sn -Sn-1 but in case of objective exams where speed matters it is better to use the former one.

so here , Sn -Sn-1 = an  , i.e. nth term.

a) apply n=2 , we get a2 not equal to 22 so the option is eliminated.

b) not clearly mentioned by you.

c)apply two a2 is 22 but it you shud check also for n =9 where it gives wrong answer so option is eliminated.

d) manually see it is right .

so option d is correct.

Please feel free to post as many doubts on our discussion forum as you can. We are all IITians and here to help you in your IIT JEE preparation.

Now you can win exciting gifts by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.

Win exciting gifts by answering the questions on Discussion Forum

4 years ago

Post Your Answer

More Questions On IIT JEE Entrance Exam

Ask Experts

Have any Question? Ask Experts
Post Question
Answer ‘n’ Earn
Attractive Gift
To Win!!!
Click Here for details
Hi I’m from bangalore. I had missed IIT with a really small margin. Now I’m in Engineering 1 st semister. I have 8 months left. How shall I plan to study? P.S: It takes a litle time to...
Coaching is a super structure providing –planned regime and expert guidance but ultimately it’s the students who have to work hard to crack the exams. 1. The students must remain...
Harishwar 5 months ago
You will face a lot problems in juggling with JEE preparation and dealing with the academic committments of your college. You need to make a trade off between the two, i.e., given somebody a...
Aziz Alam 5 months ago
I am an OCI (Overseas Citizen of India) and I have a doubt whether I am able to obtain a seat at the IITs? I've checked the bulletin released JEE MAIN website and it says, "OCI/PIO/Foreign...
OCi/PIO are not eligible for admission to these institutes through this channel, not this year atleast. There are a lot progressions going around on this issue and the ministry may decide to...
Ravi 4 months ago
I’ve signed up for MAINS under OCI nationality. It warned me about the ineligibility of NITS, IIITS, & other CFTIs, but I’m wondering whether I can get into IIT through JEE ADVANCED? Or does...
John Doe 4 months ago
WHAT BOOKS SHOULD BE PREFERRED FOR CALCULUShat books are to be prefrred for calcolus
Arihant Differential Calculus nd Integral calculus
JAinil 2 months ago
Calculus by IA Maron is a really good book.
Ram 2 months ago
when will jee mains 2014 counselling registration start ?
JEE Main 2014 Counselling Procedure - Started from July 8, 2014. Candidates can apply for online Registration, Choice filling and Choice Locking followed by Seat Allotment and admission...
Sher Mohammad 8 months ago
why coronary vein does not exist?
Hi student Where did you read this? Coronary vein exists. It drain blood from the muscular tissue of the heart and empty into the coronary sinus.
Anjali Ahuja 3 months ago
sir this year i am giving ntse exam...but i am not taking classes for sir kaise prepare karna hoga..
Most of thing will come from your school syllabus. First, you should focus on the school study, plus there is a book for NTSE exam by Tata Mcgraw hill. You should focus on the book as well....
Jitender Singh 9 months ago
View all Questions »