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In an AP: Given a = 5, d = 3, an = 50, find n and Sn. - Mathematics

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In an AP:

Given a = 5, d = 3, an = 50, find n and Sn.

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Solution

Given that, a = 5, d = 3, an = 50

As an = a + (n − 1)d,

⇒ 50 = 5 + (n - 1) × 3

⇒ 3(n - 1) = 45

⇒ n - 1 = 15

⇒ n = 16

Now, `S_n = n/2 (a + a_n)`

Sn = `16/2 (5 + 50) = 440`

Concept: Sum of First n Terms of an AP
  Is there an error in this question or solution?

APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.3 | Q 3.01 | Page 112
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