A fraction does not only say which part is colored. You can also calculate with it.
This is how you do it:
1. Divide the quantity by the lower number of the fraction. That is one single part.
2. Multiply this part by the upper number. That is how many parts you need.
Example for a quarter of 800 m: 800 : 4 = 200, so it is 200 m.
Example for three quarters of 800 m: 800 : 4 = 200 and 200 · 3 = 600 m.
If the upper number is a 1, you only need the first step.
Example
For parents
What does this exercise practice?
Working out the fraction of a quantity in two steps -- first divide by the denominator, then multiply by the numerator.
Common pitfalls
Do not divide by the upper number. You always divide by the lower number, and the unit stays the same.
How to practice at home
Ask while cooking or shopping -- half of 500 g of flour, a quarter of 2 l of juice.
Related: Fractions, Divided By