The sum of the first 20 terms of the series 1/(4 X 5) + 1/(5 X 6) + … is:

Options
- 0.209
- 2.09
- 20.9
- None of these

CORRECT ANSWER : 0.209

Discussion Board
Answer to this Problem

1/(4*5) + 1/(5*6) + .......+ 1/(23*24) (20 terms)

Formula :- 1/[a * (a+1)] = (1/a - 1/a+1)

(1/4 - 1/5) + (1/5 - 1/6) + ........+ (1/23 - 1/24)

-1/5 , +1/5 cancelled
-1/6 , +1/6 cancelled and soo on until
-1/23 , +1/23 cancelled

Then the remaining is,
= 1/4 - 1/24
= (6-1)/24
= 5/24
=0.20833333 ~ 0.209

Rekha K 10-29-2024 09:36 AM

hint

1/[a*(a+1)]=1/a - 1/(a+1)

sai 04-24-2024 12:35 PM

Answer for this problem

Answer for this problem

Kusuma Vemuri 08-8-2022 10:13 PM

solution

can u provide the answer of this.

TARUN PAL 09-13-2020 06:06 AM

Solution

can you give the solution for this problem

Ragini 11-29-2019 09:24 AM

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