Question

Dakota makes a salad dressing by combining 6 1/3 fluid ounces of oil and 2 3/8 fluid ounces of vinegar in a jar. She then pours 2 1/4 fluid ounces of the dressing onto her salad. How much dressing remains in the jar

Answer 1

We'll start by figuring out how many ounces of dressing she puts into the jar. To add together two mixed numbers with different denominators, we'll first find equivalent fractions with common denominators. 

The two fractions are $\frac{1}{3}$ and $\frac{3}{8}$. The least common denominator of 3 and 8 is 24. Let's find equivalent fractions that have 24 as the denominator for both.
For $\frac{1}{3}$, $\frac{1x8}{3x8}$ = $\frac{3}{24}$
For $\frac{3}{8}$, $\frac{3x3}{8x3}$ = $\frac{9}{24}$

Now we can add the whole numbers and equivalent fractions together.
   6 $\frac{3}{24}$
+ 2 $\frac{9}{24}$
= 8 $\frac{12}{24}$
Reduce the fraction $\frac{12}{24}$ by dividing the numerator and denominator by 12 to get the total dressing amount of 8 $\frac{1}{2}$.

Now we need to take the amount of dressing and subtract the amount that she poured out. The process will be the same as above, but we'll subtract instead of add. First, we'll find equivalent fractions using the common denominator 4.
Dressing $\frac{1}{2}$ = $\frac{2}{4}$
Poured out $\frac{1}{4}$ (This can stay the same since the denomiator is already 4.

Now we can subtract:
  8 $\frac{2}{4}$
- 2 $\frac{1}{4}$
= 6 $\frac{1}{4}$

The amount of dressing left in the jar is 6 $\frac{1}{4}$ fluid ounces.