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If sum(n=1)^(n)(2r+1)=440, then n= . . ...

If `sum_(n=1)^(n)(2r+1)=440`, then n= . . . .

A

20

B

22

C

21

D

19

Text Solution

Verified by Experts

The correct Answer is:
A
We have, `underset(r=1)overset(n)(sum)(2r+l)=440`
`implies3+5+7 . . .+(2n+1)=440`
`implies(n)/(2)[2xx3+(n-1)(2)]=440`
`impliesn(3+n-1)=440`
`impliesn(n+2)=440`
`impliesn=20`
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