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Question
In an A.P., ten times of its tenth term is equal to thirty times of its 30th term. Find its 40th term.
Solution
The general term of an A.P. is given by
tn = a + (n – 1)d
Given,
10 × t10 = 30 × t30
`=>` 10 × (a + 9d) = 30 × (a + 29d)
`=>` a + 9d = 3a + 87d
`=>` 2a + 78d = 0
`=>` a + 39d = 0
`=>` a = –39d
Now, t40 = a + 39d
= –39d + 39d
= 0
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