One pipe can fill a tank in 4 hours. A second pipe also requires 4 hours, but a third needs three hours. How long will it take to fill the tank if all three pipes are open?

Step-by-step explanation:

We will use the idea here that the first 2 pipes can get 1/4 of the job done in an hour, and that the third pipe can get 1/3 of the job done in an hour. We need to know then the number of hours it will take to fill the tank if all 3 work together. The equation looks like this:

Now we find a common denominator and solve for x. The common denominator is 12x. Multiplying everything by 12 x gives us

3x + 3x + 4x = 12 and

10x = 12 so

x = 1.2 hours

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.

the answer will be