Q. If the 7th term of HP is $\frac{1}{10}$ and the 12th term is $\frac{1}{25}$, then the 20th term is
A) $\frac{1}{41}$
B) $\frac{1}{45}$
C) $\frac{1}{49}$
D) $\frac{1}{37}$
Explanation
(c)
The corresponding terms of HP in terms of AP is 10 and 25
$\therefore T_{7} = a + 6d = 10$ … (i)
and $T_{12} = a + 11d = 25$ …(ii)
On solving Eqs. (i) and (ii), we get
$a = - 8,\ d = 3$
$\therefore\ T_{20} = - 8 + (20 - 1)3 = 49$
Then, 20th term of HP is $\frac{1}{49}$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.