³⁰Looking at the unity-fraction problem, we see that “grams” (g) will cancel from top and bottom of the unity fraction, and “ethane” will cancel from the given quantity and from the bottom of the unity fraction. This leaves “kilograms” (kg) from the given quantity and “oxygen” from the top of the unity fraction as the only units remaining after cancellation, giving us the proper units for our answer: kilograms of oxygen.