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Find the Sum of First 22 Terms of an Ap in Which D = 7 and 22nd Term is 149. - Mathematics

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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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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

Concept: Sum of First n Terms of an AP
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APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.3 | Q 7 | Page 113
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