There are 39 students in Ms. Salazar's chemistry class. If Ms. Salazar divides the class into 9 lab groups of 4 or 5 students each, what would be the number of lab groups with 5 students?

Answer:

3 groups of 5

Explanation:

if x is the number of groups of four, and y is the number of groups of five, then 4x +5y =39 (four students per group of four times the # of groups of four,   and 5 students per group times the # of groups of five, which should equal the total amount of students, 39). also, x+y=9. (number of each type of group = 9 groups total).

then, use these two equations and solve for y, by "canceling out" x. there are many ways to do this, but i'm going to use subtraction.

4x-5y=39

x+y=9

you want to change the equation

x+y=9

into

4x+4y=36

by multiplying the whole equation by four. because in order to cancel out the x, you need it to equal zero. in the first equation, its 4x.

so its now

4x-5y =39  MINUS

4x+4y=36

___________

y=3

you can check your work because the remaining 6 groups of four (24 total students) plus the 3 groups of five (15 total students) adds up to equal 36

Describe how a continental divide affects the direction of water flow over land

Some colleges are selective because:
A. they are located in metropolitan areas.
B. they do not spend time reviewing applications as thoroughly.
C. they have a high number of applicants and a limited number of
spots.
D. only a small number of students apply to them.

III.
The analogies below are word problems that consist of two word
pairs. Look at the first pair and decide how the two words relate to
each other. Then select one of the words below so the second pair of
words has the same relationship.
1. CORRUPT. MORALS
A) talented : skall B) rude intelligence C) fortunate money D) ruthless: mercy​