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Question
Find the number of terms in the A.P.: 18, `15 1/2, 13, ...., -47.`
Solution
We have been given an A.P
18, `15 1/2`, 13, .... -47.
Here, a = 18, d = `15 1/2 - 18 = -5/2` , `a_n = -47`
We will find n using
`a_n = a + (n - 1)d`
Plugging the values in the formula we get:
`-47 = 18 + (n - 1) (-5/2)`
`-47 = 18 - 5/2n + 5/2`
n = 27
Therefore, there are 27 terms in an A.P
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