Carl wants to find the product 30×56. Which of the following best explains how he can find the product mentally?
A.

He knows that 30÷5 is 6. He then multiplies 6 by 6 to get 36.
B.

He knows that 30×66is 30. He then subtracts 1 from 30 to get 29.
C.

He knows that 3×6=18. He then adds 18 and 5 to get 23.
D.

He knows that 30×16is 5. He then multiplies 5 by 5 to get 25.

Your answer will be D. He knows that 30 × 16 is 5 then multiples 5 by 5 to get 25.

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.

step-by-step explanation: