Answer :

iGreen
1 L = 1000 mL

You can use the 500 mL cup twice.

500 + 500 = 1000

Or you can use the 300 mL cup 3 times and the 100 mL cup once.

300 + 300 + 300 + 100 = 1000
Hippalectryon
Let's notice that [tex]1L=2\cdot500mL=10\cdot100mL[/tex]

Hence you can:
* take 10 times the 100-mL cup
* take 2 times the 500 mL cup.

Here are some other ways you could have done it:
* use once the 500 mL cup, once the 300 mL cup and twice the 100 mL cup
* use three times the 300 mL cup and once the 100 mL cup
* etc.