If the 7th term of a hp is 1 by 10 and the 12th term is 1 by 25 then the 20th term is?
pratik40:
its ap or gp
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We know that the general form of H.P. is
1/a + 1/(a + d) + 1(a + 2d) + ...
The 7th term = 1/(a + 6d) = 1/10 => a +6 d = 10
The 12th term = 1/(a + 11d) = 1/25 => a +11 d = 25
Solving these two equations, a = -8, d = 3
Hence 20th term = 1/(a+19d) = 1/[-8 + 9(3)] = 1/49
1/a + 1/(a + d) + 1(a + 2d) + ...
The 7th term = 1/(a + 6d) = 1/10 => a +6 d = 10
The 12th term = 1/(a + 11d) = 1/25 => a +11 d = 25
Solving these two equations, a = -8, d = 3
Hence 20th term = 1/(a+19d) = 1/[-8 + 9(3)] = 1/49
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If the 7th term of a hp is 1 by 10 and the 12th term is 1 by 25 then the 20th term is?
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