Convert km per second to parsec per year ?

Question

Hi everyone, i need to convert 15000 km per second to parsecs per year. I know that 1 pc = 3.1 x 10 to the 13 km and that 1 yr = 3.2 x 10 to the 7 seconds, but my brain won't let me join the dots. Pls help

Answer 1

Work with your conversion factors by setting up an equation that cancels out your original engineering units and leaves you with a value having the engineering units that you desire.

1.5*10^4 km/sec * (3.2*10^7 sec/1 yr) * (1 pc/3.1*10^13 km) =

(1.5*10^4 * 3.2*10^7 / 3.1*10^13) pc/yr.

km and sec cancel out and you are left with engineering unit of pc/yr