It is 4 mm. If you wanted it expressed in metres or kilometres, you should have said so in the question, not left it for us to guess.
As wide as 4mm on a ruler
fraction of 4 cm is 4mm = 1/101 cm = 10mm4 cm = 40mm4mm/4cm = 4mm/40mm = 4/40 or 1/10
Approx 0.1575 inches.
Oh, dude, let me break it down for you. So, 2cm is the same as 20mm, right? And if 4mm is a part of that 20mm, then the fraction would be 4/20, which simplifies to 1/5. So, 4mm of 2cm is like 1/5. Easy peasy, right?
It is simply: 4/1 mm as an improper fraction