Question

the sum of first ten terms of ap 2.5.8.11. is​

Answer 1

Answer :-

Sum of first 10 terms = 155

Step-by-step explanation :-

Given:

• First term = a = 2
• Common difference = d = 5 - 2 = 3
• Number of terms = n = 2

To find:

Sum of first 10 terms = ?

Formula used:

Sₙ = n/2 [2a + (n - 1)d]

Solution:

Substitute the given values in the above formula.

Sₙ = 10/2 [(2 × 2) + (10 - 1)3]

↠ Sₙ = 5 [4 + 9(3)]

⇢ Sₙ = 5 [4 + 27]

➪ Sₙ = 5 (31)

➪ Sₙ = 155

∴ Sum of first 10 terms = 155

Answer 2

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Given :

AP : 2,5,8,11,...

To find :

• Sum of first ten terms of given AP

Solution :

From AP : 2,5,8,11,..

First term (a) = 2

Common difference(d) = 5-2 = 3

Number of terms(n) = 10 [the no. of terms to find sum]

Sum of n terms in an AP

Sn=n/2[2a+(n-1)d]

Sn=10/2[2×2+(10-1)3]

Sn=5[4+9(3)]

Sn=5[4+27]

Sn=5[31]

Sn=155

Sum of first ten terms of given AP is 155.