Question

a parsec a unit of length used in astronomy is 1.9x10^13 miles the meab distance of a certain planet from the sun is 1.3x10^7 miles. how many parsecs is this planet from the sun?

Answer 1

For this you can use the rule of three, like this

$\begin{gathered} 1\text{ parsec}\rightarrow1.9\cdot10^{13}\text{ miles} \\ x\text{ parsec }\rightarrow\text{ 1.3}\cdot10^7\text{ miles} \\ x=\frac{1\text{ parsec }\cdot1.3\cdot10^7\text{ miles}}{1.9\cdot10^{13}\text{ miles}} \\ x=\frac{1.9}{1.3}\cdot10^{7-13}\text{ parsecs} \\ x=1.46\cdot10^{-6}\text{ parsecs} \end{gathered}$

Therefore, this planet is 1.46x10 ^ -6 parsecs from the sun.