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प्रश्न
In an A.P., ten times of its tenth term is equal to thirty times of its 30th term. Find its 40th term.
उत्तर
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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