Find the sum of all numbers between 200 | Class 11 Mathematics Chapter Sequence and Series, Sequence and Series NCERT Solutions

Question:

Find the sum of all numbers between 200 and 400 which are divisible by 7.

Answer:

The numbers lying between 200 and 400, which are divisible by 7, are

203, 210, 217, … 399

∴First term, a = 203

Last term, l = 399

Common difference, d = 7

Let the number of terms of the A.P. be n.

∴ a_n = 399 = a + (n –1) d

⇒ 399 = 203 + (n –1) 7

⇒ 7 (n –1) = 196

⇒ n –1 = 28

⇒ n = 29

$therefore space S subscript 29 space equals space 29 over 2 space open parentheses 203 space plus space 399 close parentheses space space space space space space space space space space space space space equals space 29 over 2 space open parentheses 602 close parentheses space space space space space space space space space space space space space equals space open parentheses 29 close parentheses open parentheses 301 close parentheses space space space space space space space space space space space space space equals space 8729$

Thus, the required sum is 8729.

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Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

Read the question carefully and focus on the core concept being asked.
Reference examples and data from the chapter when answering questions about Sequence and Series.
Review previous year question papers to get an idea of how such questions may be framed in exams.
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Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Comments

Harsh
2019-08-22 21:32:16

Good

saranya
2019-02-18 18:52:33

ummma thank you

Neelam
2019-01-07 13:03:24

But how I know that first no. Is 203

David N Maikundu
2018-11-09 16:44:45

thank you great elucidation

David N Maikundu
2018-11-09 16:32:27

wonderfull explanation

Shilpa
2018-09-20 12:53:07

Thank you for your help

DHARMAPADA KARUA
2018-06-03 11:06:42

Good solution.

Puru
2017-10-10 21:25:27

Thanks for the explanation

shethra krishna
2016-11-16 07:34:16

it was a wonderful explanation

karthik
2016-10-12 14:20:48

Good explanation

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Welcome to the NCERT Solutions for Class 11 Mathematics - Chapter . This page offers a step-by-step solution to the specific question from Excercise 5 , Question 4: Find the sum of all numbers between 200 and 400 which are divisible by 7.....

Find the sum of all numbers between 200 | Class 11 Mathematics Chapter Sequence and Series, Sequence and Series NCERT Solutions

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