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If $\log _{10} 7=0.8451$, then the position of the first significant figure of $7^{-20}$ is
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Verified Answer
The correct answer is:
17
Let $x=7^{-20}$
$$
\begin{aligned}
\log _{10} x &=-20 \log _{10} 7 \\
&=-20(0.8451) \\
&=-16.902
\end{aligned}
$$
Hence, the first significant figure is $17 .$
$$
\begin{aligned}
\log _{10} x &=-20 \log _{10} 7 \\
&=-20(0.8451) \\
&=-16.902
\end{aligned}
$$
Hence, the first significant figure is $17 .$
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