Question

how many terms of an AP 1,4,7 are needed to give the sum 1335​

Answer 1

Step-by-step explanation:

In the series

a = 1

d = +3

Sn = 1335

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

1335 = n/2(2*1 + (n-1)3

1335 = n/2 (2 + 3n -3)

2670 = n(3n -1)

3n² - n - 2670 = 0

on solving the quad. equation

n= -89/3 & 30

n can't be negative

therefore answer = 30

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Answer 2

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