Pls tell sol for 5,6,7

Solution
The solution/s to your 1st query (Q5) has been provided below:
Q5.
Given,
the distance of the nearest star, Proxima Centauri from the earth is $d=4.0\times {10}^{13} km$.
1 light year is the distance travelled by light in 1 year.
Thus,
$$\begin{gathered} 1 light year=c\times t=3\times {10}^8\frac{m}{s}\times 1year=3\times {10}^8\frac{m}{s}\times 1year\times 365\frac{days}{year}\times 24\frac{hours}{day}\times 3600\frac{sec}{hour}=94608000\times {10}^8 m. \\ Thus, \\ d=4.0\times {10}^{16}m=\frac{4.0\times {10}^{16}m}{94608000\times {10}^8{\displaystyle \raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$light year$}\right.}}=4.227 light year\approx 4.2 light year \end{gathered}$$

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