$6 \cdot 52$ if $\lg 2=0.3010$ and $\lg 3=0.4771$. When $3^{x+3}=135$, the value of $x$ is approximately
(A) 5 .
(B) 1.47 .
(C) 1.67 .
(D) 1.78 .
(E) 1.63 .
(5th American High School Mathematics Examination, 1954)
[Solution] From $3^{x+3}=3^{3} \cdot 3^{x}=135$, we have $3^{x}=5$. Taking the logarithm on both sides, we get $x \lg 3=\lg 5$, so $x=\frac{\lg 5}{\lg 3}=\frac{\lg \frac{10}{2}}{\lg 3}=\frac{1-\lg 2}{\lg 3} \approx 1.47$. Therefore, the answer is $(B)$.