Q. If $\log_{10}{7 = 0.8451}$, then the position of the first significant figure of $7^{- 20}$ is
A) 16
B) 17
C) 20
D) 15
Explanation
(b)
Let $x = 7^{- 20}$
$\log_{10}{x = - 20\log_{10}7}$
$= - 20(0.8451) = - 16.902$
Hence, the first significant figure is 17
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.