Atank can be filled by three pipes separately in 20,30,and 60 minutes respectively. in how many minutes can it be filled by the three pipes acting together

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.

i think it might be a but you might want a second opinion

68719476736

step-by-step explanation:

8*8*8*8*8*8*8*8*8*8*8*8=68719476736

you meant circumference well the answer is:

17.27876 miles

area is 23.7583

the radius is 2.75 miles

hope this hmu if needed.