Question

find the sum of first 30 terms of ap ,2+5+8........​

Answer 1

Answer:

sn= n\2 (2a +(n-1) d)

= 1095

Step-by-step explanation:

s30 = 30\2 (2(2) + 30-1 (3))

= 1095

I try my level best tq

Answer 2

The sum of first 30 terms of the AP 2 + 5 + 8 + . . . is 1365

Given :

The AP 2 + 5 + 8 + . . .

To find :

The sum of first 30 terms of the AP

Formula :

Sum of first n terms of an arithmetic progression

$\displaystyle \sf S_n= \frac{n}{2} \bigg[2a + (n - 1)d \bigg]$

Where First term = a

Common Difference = d

Solution :

Step 1 of 3 :

Write down the given AP

Here the given AP is 2 + 5 + 8 + . . .

Step 2 of 3 :

Write down first term and common difference

First term = a = 2

Common Difference = d = 5 - 2 = 3

Step 3 of 3 :

Calculate sum of first 30 terms of the AP

Number of terms = n = 30

∴ The sum of first 30 terms of the AP

$\displaystyle \sf = \frac{n}{2} \bigg[2a + (n - 1)d \bigg]$

$\displaystyle \sf = \frac{30}{2} \bigg[(2 \times 2) + (30 - 1) \times 3 \bigg]$

$\displaystyle \sf = 15 \times \bigg[4 + 87 \bigg]$

$\displaystyle \sf = 15 \times 91$

$\displaystyle \sf = 1365$

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