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Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.

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Question

Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.

Sum
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Solution

d = 7

a22 = 149

S22 = ?

an = a + (n − 1)d

a22 = a + (22 − 1)d

149 = a + 21 × 7

149 = a + 147

a = 2

`S_n = n/2(a+a_n)`

= `22/2(2+149)`

= 11(151)

= 1661

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Chapter 5: Arithmetic Progressions - EXERCISE 5.3 [Page 69]

APPEARS IN

NCERT Mathematics [English] Class 10
Chapter 5 Arithmetic Progressions
EXERCISE 5.3 | Q 7. | Page 69
ML Aggarwal Understanding Mathematics [English] Class 10 ICSE
Chapter 9 Arithmetic and Geometric Progressions
Exercise 9.3 | Q 9
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