5 students are missing from a class. That is 1/4 of the class. How many total students. Write the equation

Question

I know the answer is 20 but I can't figure out how to write the equation

Answer 1

 

Let x be the number of students in the class.

 

We need to figure out the value of x then, agreed?

 

We are told that 5 is 1/4 of the class size.  Writing this

fact in terms of our  unknown  x  gives:

 

                5 = (1/4)x          ("is" in a word problem means "=" when writing equations)

             5*4 = (1/4)*4*x    (multiply both sides by 4, we're trying to get one x  by itself)

               20 = 1x               (done, 20=1x can be written 1x=20 so x=20, right?)

 

There is nothing special about the use of 'x', it just holds the place of the unknown.  We could've used any letter or even a word or other symbol.

 

Hope this helps you.

 

            

 

 

Answer 2

S = number of total students registered in that class

 

1/4 of S means you divide S by 4 and the result is 5 (that is what the problem says)

 

Easy to write the equation...isn't it? Instead of S you may use X if you want.