If 4 grams of water vapor are present in a cubic meter of air that can hold a maximum of 10 grams, what is the relative humidity?

40%

Explanation:

The relative humidity refers to the ratio of water vapor present in the air and the maximum amount of water vapor that the air can hold at a given temperature.

Mathematically, it can be expressed as;

Relative humidity = amount of water vapor in the air/maximum amount of water vapor the air can hold x 100%

In this case,

Amount of water vapor in the air = 4 grams

Maximum amount of water vapor the air can hold = 10 grams

Relative humidity = 4/10 x 100%

                               = 40%

Hence, the relative humidity is 40%.