The half-life of radon-222 is 3.8 days. if a sample currently contains 3.1 grams of radon-222, how much radon-222 did this sample have 15.2 days ago? a 12.4 grams b 47.1 grams c 49.6 grams d 57.8 grams

The   number  of grams of  radon 222 did it have 15.2  ago was  49.6 grams( answer  C)

 calculation

             that is  divide 15.2/ 3.8 = 4 half life

therefore  3.8 days ago  it was  3.1 x2 =  6.2 grams

                  7.6 days ago  it was 6.2 x2 = 12.4 grams

                   11.4  days  ago it was 12.4  x2=  24.8  grams

                  15.2  days  ago  it was  24.8 x2=49.6 grams

plants need sunlight, water, and carbon dioxide to make food. plants use the raw materials of water, nutrients they absorb from soil, and carbon dioxide to make sugars the plant can use. energy from the sun and chlorophyll are also needed.

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .