Hi Dalia;

**1) what is the room's volume in cubic meters? in liters?**

volume=(length)(width)(height)[(0.3048 meters)/(1 foot)]

volume=(18 feet)(15 feet)(8.5 feet)[(0.3048 meters)^{3}/(1 foot)^{3}]

Let's first notice that the unit of feet is multiplied three times in the numerator, and the unit of foot is to the exponential of three in the denominator. These cancel...

volume=(18 feet)(15 feet)(8.5 feet)[(0.3048 meters)^{3}/(1 foot)^{3}]

volume=(18)(15)(8.5)(0.3048 meters)^{3}

Now that our units are aligned, we may calculate...

volume=699.516 meters^{3}

In liters...

1,000 liters=1 meter^{3}

volume=(699.516 meters^{3})[(1,000 liters)/(1 meter^{3})]

The unit of cubic-meters is in the numerator and denominator. It cancels.

volume=(699.516 meters^{3})[(1,000 liters)/(1 meter^{3})]

volume=(699.516)(1,000 liters)

volume=699,516 liters

**assume the density of air is 1.2 g/L and that the room is empty of furniture.**

699,516 liters[(1.2 grams)/(1 liter)]

The unit of liters is in the numerator and denominator. It cancels...

699,516 liters[(1.2 grams)/(1 liter)]

699,516(1.2 grams)

839,419.2 grams

1000 grams=1 kg

839,419.2 grams[(1 kg)/(1000 g)]

0.8394192 kilograms

0.8394192 kilograms[(2.20462 pounds)/(1 kilogram)]

The units of kilograms cancels...

1.850600356704 pounds