How Many Bags

You have 2/3 of a litre of juice and pour it into glasses that hold 1/6 of a litre each. How many glasses can you fill? The question is how many sixths fit into 2/3, and that is a division.

Pick a letter, g for glasses: $g = \frac{2}{3} \div \frac{1}{6}$. On the board you type the division with a slash, and it shows as a fraction bar. Flip and multiply: $g = \frac{2}{3}\cdot 6$, which is $g = \frac{12}{3}$, and that is $g = 4$. Four glasses.

Check it by going the other way: 4 glasses of $\frac{1}{6}$ litre is $4\cdot \frac{1}{6}$, which is $\frac{4}{6}$, the same as $\frac{2}{3}$. Every bit of the juice is used.