Several different sets of skills and knowledge needed for these questions. Firstly knowledge of measurements eg that there are 1000 metres in a kilometre, 1000 ml in a litre etc, as well as a couple of Imperial measures thrown in as an extra challenge.
Secondly, to be able to write 600ml as a fraction of 1litre eg 600/1000.
Thirdly to be able to simplify fractions eg 600/1000 is equivalent to 6/10.
Watch out for question 11 as it is easy to think that there are just 100 sq cm in a square metre when, in fact, it is many, many more!