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First term of an A,P is -5 and its last ...

First term of an A,P is -5 and its last term is 45 lf the sum of these terms is 120 find the number of terms.

Text Solution

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`a = -5 `
`l= 45`
`S_n = n/2[a+l]`
`n/2(-5 +45)= 120 `
`n/2(40) = 120`
`n= 6`
Answer
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