kaja has 1 2/3 gallons of milk. She used 1/4 of milk for breakfast. How much milk does she have left?

Question

kaja has 1 2/3 gallons of milk. She used 1/4 of milk for breakfast. How much milk does she have left?

Answer 1

1 2/3 = 1 8/12 milk starting

 

If she uses 1/4 = 3/12 of it so subtract like denominators:

 

1 8/12 - 3/12 = 1 5/12 gallons left. 

 

(5/12 doesn't reduce further.)  

 

Answer 2

[very important note:  Did kaja use "1/4 gallon of milk" or "1/4 of milk" for Breakfast.  That makes a big difference.]

This is a simple subtraction problem, but it includes a fraction of the total.  In word(story) problems, the word "of" usually means multiply.
     left  =   total    -       used
                 1 2/3    -      1/4*(1 2/3)
                  5/3    -      (1/4)*(5/3)              [use an improper fraction]
                20/12   -   5/12                        [we need a common denominator]
                  15/12
                   5/4
      left  =   1 1/4 gallons                 [make proper number again]

 

You could also compute this as:

                1 2/3   -      (1/4)*(1 2/3)

               (4/4)*(5/3)   -  (1/4)*(5/3)

                 (3/4)*(5/3)

                    (5/4)                            [the 3 cancels out]

                    1 1/4 gallons