How much water should be added to 8 quarts of 90% antifreeze to get a 30% solution?

16 quarts

Step-by-step explanation:

Let's say x is the volume of water.

Initially, the amount of antifreeze is the concentration times the volume: 0.90 (8).

After the water is added, the amount of antifreeze is the new concentration times the new volume: 0.30 (8 + x).

Since the amount of antifreeze doesn't change, we can set these equal and solve for x.

0.90 (8) = 0.30 (8 + x)

7.2 = 2.4 + 0.30 x

4.8 = 0.30 x

x = 16

16 quarts of water should be added.

introduction, methodology, results, discussion

step-by-step explanation:

an observational study is one which consists of actual observation to record data and then analyse the data.

there are a number of factors that should be analyzed before starting an observational study.

the main four factors are:

i) introduction:   this should be analysed to check whether the purpose of the study is correctly established and the data recorded are appropriate for the study

methodology:   the method of collecting the data, such as whether randomly selected, and whether sample size matches with the population to be studied, whether questions asked are easy to answer by common men, etc.

results: then results such as summary of data with comments should be studied thoroughly

discussion:   the last is the discussion, this can be either by management people or persons who are all interested , etc.