if there are 245 seventh grade in the school,how many can be expected to prefer chocolate milk ?

Question

                  Drink                    students

             chocolate                      15

              soda                            12

              milk                              6

               water                          2

Answer 1

Hi!

 

If we add up all the people sampled, we get 15+12+6+2 = 35 people total

 

That means 15 out of 35 people prefer chocolate milk.

 

but we want to know how many people like chocolate milk out of 245 people.  So we set up a proportion

 

It's very easy

 

15 like milk out of 35 people, which we can express as a fraction:

15/35

 

or

 

15

---

35

 

 

we can also use a variable like 'n' to make a similar fraction for all 245 seventh graders:

 

n/245

 

or

 

 n

---

245

 

to solve for 'n', we set the two fractions equal to each other (this is what is know as a proportion) and use cross multiplication to solve for 'n':

 

15         n

---   =  ---

35        245

 

 

15*245 = n*35

 

3675 = n * 35

3675/35 = n

n = 105

 

that means that, based on our survey sample, we can expect about 105 seventh graders to prefer chocolate milk.