When multiplying or dividing, make sure you know how many sigfigs are in your factors. The factor with thes least amount of sigfigs is the one you want to know. When you get your final answer, make sure you have the same amount of sigfigs that the factor had.
Example
34.07 has 4 sigfigs
6.4 has only two
34.07x6.4=218.048
But we only want two sigfigs so 218.048 becomes 220