Question

In an ap of 1st term is 2 ,and sum of 1st 5 terms is one foueth of next 5 terms.Find the sum of first 20 terms

Answer 1

$\underline{\underline{\Huge\mathfrak\red{Answer:}}}$

Given an AP whose first term is 2
To find: 20th term of an AP
It is given that the sum of the first five terms is one-fourth of the next 5 terms

So,

20a + 40d = 5a + 35d
15a + 5d = 0

Substituting a as 2

We get d = - 6

Hence 20th term is a + 19d = - 112

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