Fill in the blanks to make the statements true:
If the thickness of a pile of 12 cardboard sheets is 45 mm, then the thickness of a pile of 240 sheets is …………. Cm.
The thickness of a pile of 12 cardboard sheets = 45mm
∴ the thickness of a pile of 1 cardboard sheet = 
mm
So, the thickness of a pile of 240 cardboard sheets
⇒ 
⇒
= 
36