logo

Ask Questions, Get Answers

 
X
 Search
Want to ask us a question? Click here
Browse Questions
Ad
Home  >>  JEEMAIN and AIPMT  >>  Mathematics  >>  Class11  >>  Sequence and Series
0 votes

In the series 2,10,50 ------ the number of terms required to make a sum of 7812 is

$\begin{array}{1 1} 5 \\ 6\\ 10 \\ 70 \end{array}$

Can you answer this question?
 
 

1 Answer

0 votes
Answer : (b) 6
Explanation : 2,10,50 ------ is a with a=2 , r=5
$S_{n}=\frac{a(r^n-1)}{r-1}=\frac{2(5^n-1)}{5-1}=7812$
$5^n=(7812*2)+1=15625=5^6$
$n=6.$
answered Jan 3, 2014 by yamini.v
 

Related questions

Ask Question
student study plans
x
JEE MAIN, CBSE, NEET Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App
...