Dakota State University
Madison, SD, USA

Math Skills

Practice
Answer

1. State the number of significant digits in the following numbers:

   b) $42,850,000	Four (4) significant digits. The trailing four
			zeros are there just to indicate where the
			decimal point goes. If the number were written in
			scientific notation, it would be $4.285 x 10^7. The
                        zeros disappeared. If the zeros disappear when a
                        number is converted to scientific notation, then
                        the zeros are not significant.

			If the zeros were meant to be significant, the
			number would be written as $42,850,000., where
			the decimal point indicates the number was 
			measured to the nearest dollar rather than to the
			nearest ten thousand dollars.

                        To indicate, say, six significant digits, write the
                        number in scientific notation with trailing zeros:
                        $4.28500 x 10^7. The two zeros are not needed to 
                        indicate where the decimal point goes. Therefore
                        they must be there to indicate precision. This
                        format indicates the number was measured to the
                        nearest hundred dollars.

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