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Question
The first and last terms of an A.P. are 1 and 11. If the sum of its terms is 36, then the number of terms will be
Options
5
6
7
8
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Solution
In the given problem, we need to find the number of terms in an A.P. We are given,
First term (a) = 1
Last term (an) = 11
Sum of its terms Sn = 36
Now, as we know,
`S_n = (n/2) ( a + l)`
Where, a = the first term
l = the last term
So, we get,
`36 = (n/2)(1 + 11)`
`36(2) = 12n`
`n = (36(2))/12`
n = 6
Therefore, the total number of terms in the given A.P. is n = 6
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