What is the measurement 111.009 mm rounded off to four significant digits?

a. 111mm

b. 111.0 mm

c. 111.01mm

d. 110mm

To 4 significant figures, the correct answer should be B. 111.0 mm.

111.009 mm

It has:

6 significant figures.

As the zero to the left of 9 is less than 5.

So we have to get rid of it, and it is cancelled and 9 with it also get cancelled.

So, it will become,

111.0 mm

It has 4 significant figures:

*3 nonzero digits

*1 trailing zero

So according to above explanation,

b. 111.0 mm, is the correct answer.