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If the first, second and last terms of a...

If the first, second and last terms of an arithmetic series are a,b and c respectively , then the number of terms is

A

`(b+c-2a)/(b-a)`

B

` (b+c+2a)/(b-a)`

C

` (b+c - 2a)/(b+a)`

D

`(b+c+2a)/(b+a)`

Text Solution

Verified by Experts

The correct Answer is:
a
Since, `l = A +(n-1)d `
` :. C = a+(n-1)(b-a)" " [ :' d = a_(2) - a_(1)]`
` rArr (n-1) = (c-a)/(b-a)`
` rArr n = (b+c-2a)/(b-a)`
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