Ok let us assume x= the width of the table top the length is 4 times the width meaning we are multiplying 4 and the width which is x length = 4x your first equation would be the following: 4x+4x+x+x= whatever the perimeter is if you drew a rectangle it would help you understand the above.
this represents the perimeter of the tabletop because we know the width is x. if you drew the rectangle there wouldn't be 1 width. opposite to the width is another line. same with the length. the length is 4x again there are 2 because in a rectangle there are 2 sets of parallel lines. that is why your equation would be 4x+4x+x+x= whatever the perimeter is- you could simplify this equation and write: 10x= whatever the perimeter is x basically means 1x but in math we generally don't write that because we tend to write most things in simplest for. hope this helps :)
To take a sample to estimate the mean height of all students at a university and that the value you reach is statistically valid you need the sampling method to be random and representative of the whole population, in this example, all university students.
a. Measure the heights of 50 students found in the gym during basketball intramurals.
This method is not the best because you would be sampling only basketball players leaving all other students of the university outside, i.e. your sample will not be representative of all the students, just the ones that play basketball.
b. Measure the heights of all engineering majors.
This method is not good, the sample only represents engineering mayors meaning that it does not include the students of any other subjects.
c. Measure the heights of the students selected by choosing the first name on each page of the campus phone book.
With this method you choose students regardless of the sport or major they're are taking, it is more representative of the population of university students, of the three options, this is the best one.
