Final Answer 3.31 What Numbers of cm are known? First, We can see that it is between 3 and 4 cm. Secondly we can see that it is between the .3 and .4 line. So we are certain about 3.4 What Numbers of cm are uncertain. We are not sure how far past the .3 line it is so we guess. Maybe 0, maybe 1 You try this one! Ask Mrs. Machart for the answer