See examples to the left. For numbers in scientific notation , cases 1 through 3 are used to determine the number of significant figures. In both case 4 and cased 5 above, the zeroes are present to pad the positions to place the true numeric value in its proper decimal places. They have nothing to do with the measurement. This problem can sometimes be eliminated by re-scaling the units, but often this is not possible.
Scientific notation removes the ambiguities caused by place-holding zeroes.
Manipulating Significant Figures Measurements are often combined by multiplying, dividing, adding, or subtractingto compute a property. In these instances, we need a systmatic way to keep track of how the significant figures are treated under these operations. When multiplying or dividing significant figures, the answer contains as many significant figures as the value with the fewest. Multiply or divide the values as normal. Determine the number of significant figures in the multiplicands.