Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • NCERT
  • Find the sum of the following APs: (iv) 1 by 15, 1 by 12, 1 by 10, ..., to 11 terms

Q : 1      Find the sum of the following APs:

              (iv)   \small \frac{1}{15},\frac{1}{12},\frac{1}{10},...,  to   \small 11  terms.

Answers (1)

best_answer

Given AP is 
 \small \frac{1}{15},\frac{1}{12},\frac{1}{10},...,  to   \small 11  terms.
Here, a = \frac{1}{15} \ and \ n = 11
And
d = a_2-a_1=\frac{1}{12}-\frac{1}{15}= \frac{5-4}{60}= \frac{1}{60}
Now, we know that 
S = \frac{n}{2}\left \{ 2a+(n-1)d \right \}
\Rightarrow S = \frac{11}{2}\left \{ 2\times \frac{1}{15} +(11-1)(\frac{1}{60})\right \}
\Rightarrow S = \frac{11}{2}\left \{ \frac{2}{15} +\frac{1}{6}\right \}
\Rightarrow S = \frac{11}{2}\left \{ \frac{9}{30}\right \}
\Rightarrow S =\frac{99}{60}= \frac{33}{20}
Therefore, the sum of AP  \small \frac{1}{15},\frac{1}{12},\frac{1}{10},...,  to   \small 11  terms. is \frac{33}{20}

Posted by

Gautam harsolia

View full answer

Similar Questions

Trending Articles/News

anam-khan

CBSE Class 10, 12 syllabus 2024-25 out; board restores two-level mathematics rule
anam-khan

CBSE Class 10 board exam 2024 passing criteria, eligibility for compartment; all you need to know

Latest Question