There is one significant figure in the number .001. Leading zeroes, which only serve to indicate the position of the decimal, are never significant.
001 has one significant digit, so the answer can only have one. 1.2 x 001 = 1
The two numbers mentioned in the question have four significant figures (often called significant digits). If you wish to check your knowledge of sig-digs, check out the following link: http://science.widener.edu/svb/tutorial/sigfigures.html
231.57 has five significant figures/numbers. All the numbers in 231.57 are significant.
The figure 18.03 has a total of four significant numbers
Three. All nonzero numbers are significant, and any zeros in between significant numbers are significant.
002+002+001=005
Because 10.00400 is 10.004, this has five significant digits (numbers).
3 significant figures.
It has five significant figures.
7 significant figures.
3 significant figures.