What factors affect water quality?

Explained below:

Explanation:

Water quality is determined in terms of the physical, chemical and biological content of water. The quality of water of lakes and rivers variates with the seasons and also geographic areas, still in the absence of pollution. There are  so many factors  which affect water quality are as follows :

Pesticides

Temperature

Runoff

Sedimentation

Erosion

pH

Dissolved oxygen

Pesticides

Litter and rubbish

Decayed organic materials

Toxic and hazardous substances

Oils, grease, and other chemicals

their crystal patterns have been disrupted by stress

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form