We know from earlier posts (see the previous one here<\/a>) why significant figures are needed and how to tell when zeros are significant. Now, we’ll discuss how to report the result of a calculation to the correct number of significant figures.<\/p>\n Remember that, “on sight”, all nonzero digits are significant. The rules for zeros, once again, are covered here<\/a>. However, once you do a calculation, you must apply other rules to determine how many significant digits are in the answer.<\/p>\n With mutliplying and dividing, the method is simple:<\/p>\n 1)\u00a0 Decide which input number has the least number of significant figures.<\/p>\n 2)\u00a0 The least number from 1) is the proper number of significant figures for your answer.<\/p>\n Putting it a different way:\u00a0 the correct number of significant figures for the answer is how many the input with the least of them has.<\/p>\n Consider an example:<\/p>\n 75.04 x 0.407<\/p>\n We know that 75.04 has four significant digits, while 0.407 has\u00a03.\u00a0 Our answer must then have three significant digits.<\/p>\n Of course,\u00a0as often happens,\u00a0the calculator gives us more than the proper number of significant digits:<\/p>\n 75.04 x 0.407 = 30.54128<\/p>\n We round our answer to three significant digits:<\/p>\n 30.54128 \u2248 30.5<\/p>\n Just to review:\u00a0 We were multiplying.\u00a0 One input number had four significant digits and one had three.\u00a0 Therefore, we rounded our answer to three significant digits.<\/p>\n Here’s another example:<\/p>\n 0.5695 \u00f7 1.7 = 0.335<\/p>\n We know that 0.5674 has four significant digits\u00a0while 1.7 has only two.\u00a0 Our answer, therefore, should have two significant digits:<\/p>\n 0.335 \u2248 0.34<\/p>\n (Since the\u00a0next digit is 5 or more, we round up to 0.34.)<\/p>\n The\u00a0method explained in this post\u00a0applies to multiplying and dividing with significant digits.\u00a0 Adding and subtracting use a different method, which will be covered in a future post.<\/p>\n