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Question
In an A.P., a = −36, d = 18 and l = 36, then n is ______.
Options
10
5
15
20
MCQ
Fill in the Blanks
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Solution
In an A.P., a = −36, d = 18 and l = 36, then n is 5.
Explanation:
Let nth be the last term.
By formula,
an = a + (n − 1)d
Substituting values we get:
⇒ 36 = −36 + (n − 1)18
⇒ 36 = −36 + 18n − 18
⇒ 36 + 36 + 18 = 18n
⇒ 18n = 90
⇒ n = `90/18` = 5.
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