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Question
Fill in the blank in the following table, given that a is the first term, d the common difference, and an nth term of the AP:
| a | d | n | an |
| -18.9 | 2.5 | ______ | 3.6 |
Solution
| a | d | n | an |
| -18.9 | 2.5 | 10 | 3.6 |
Explanation:
a = -18.9, d = 2.5, an = 3.6, n = ?
We know that,
an = a + (n - 1) d
3.6 = -18.9 + (n - 1) 2.5
3.6 + 18.9 = (n - 1) 2.5
22.5 = (n - 1) 2.5
`("n" - 1) = (22.5)/2.5`
n - 1 = 9
n = 10
Hence, n = 10
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