What is the full answer to this problem 39.37/0.90

Consider a culture medium on which only gram-positive organisms such as staphylococcus aureus colonies can grow due to an elevated nacl level. a yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the ph as a result and changing the color of a ph indicator chemical. this type of medium would be referred to as a differential and enrichment culture.

Why is it that 85.48 rounded to two significant figures is 85 and not 86?

Amatch has about 21 milligrams of red phosphorus coating the tip. how many atoms of phosphorus is this?