Math, asked by tinojtthomas, 9 months ago

5,10,15 is an arithmetic progression find the sum of first 21 digits

Answers

Answered by warylucknow
0

The sum of the first 21 terms of the AP is 1155.

Step-by-step explanation:

The sum of first n terms of an AP is:

S_{n}=\frac{n}{2}[2a+(n-1)d]

Here,

a = 5

d = 5

n = 21

Compute the sum of first 21 terms of an AP as follows:

S_{21}=\frac{21}{2}[(2\times 5)+(21-1)(5)]

     =\frac{21}{2}\times [10+(20\times 5)]\\

     =\frac{21}{2}\times 110

     =1155

Thus, the sum of the first 21 terms of the AP is 1155.

Learn more:

https://brainly.in/question/7469347

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