What does 0.9 cm mean? It is the same as __________ mm. We can also say this is nine-tenths of a cm. Right?
As the last statement of the question suggests 0.9 cm is nine-tenth of a centimeter.
1 cm=10 mm
So,
0.9 cm=0.9×10 mm
=9 mm
So, 0.9 cm is same as 9 mm.