In an AP: Given a = 5, d = 3, an = 50, find n and Sn. - CBSE Class 10 - Mathematics

In an AP:

Given a = 5, d = 3, a_n = 50, find n and S_n.

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)`

S_n = `16/2 (5 + 50) = 440`

Is there an error in this question or solution?

Chapter 5: Arithmetic Progressions
Ex. 5.30 | Q: 3.01 | Page no. 112

Solution In an AP: Given a = 5, d = 3, an = 50, find n and Sn. Concept: Sum of First n Terms of an AP.