Of the 800 seventh grade students and 640 eighth grade students at Knox Middle School, 90 students will be chosen at random to attend an assembly.

Which of the following would be a representative sample of the number of seventh and eighth grade students at the school?

50 7th grade and 40 8th grade

Step-by-step explanation:

1. add to get total number of students, 1440

2. find percentage of total that are 7th grade students and 8th grade student:

640/1440 = ~45% (are 7th grade)

800/1440 = ~55% (are 8th grade)

3. 55% of 90 is 50, and 45% of 90 is 40

whole numbers.

step-by-step explanation:

we are given the average monthly rainfall (in millimeters) model r(m) for the years 1900-2009 as a function of the month number m.

as we can see m is taken for the number of months for years 1900-2009.

we know that number of months can't be a negative number or decimal number or a fraction.

so, the number of months could be only positive whole numbers.

therefore, whole numbers is more appropriate for the domain of r.