Answer:
40%
Step-by-step 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%.