Constants | Periodic Table Learning Goal: To practice Tactics Box 1.6 Using Significant Figures. You can think of a significant figure as being a digit that is reliably known. For example, a length measurement of 6.2 cm has two significant figures, the 6 and the 2. The next decimal place-the one-hundredths-is not reliably known and is thus not a significant figure. TACTICS BOX 1.6 Using significant figures. 1. When multiplying or dividing several numbers, or when taking roots, the number of significant figures in the answer should match the number of significant figures of the least precisely known number used in the calculation. 2. When adding or subtracting several numbers, the number of decimal places in the answer should match the smallest number of decimal places of any number used in the calculation. 3. Exact numbers are perfectly known and do not affect the number of significant figures an answer should have. Examples of exact numbers are the 2 and the a in the formula C = 2nr for the circumference of a circle. 4. It is acceptable to keep one or two extra digits during intermediate steps of a calculation, to minimize rounding error, as long as the final answer is reported with the proper number of significant figures. 5. Examples and problems in this textbook will normally provide data to either two or three significant figures, as is appropriate to the situation. The appropriate number of significant figures for the answer is determined by the data provided. Determining the proper number of significant figures is straightforward, but there a few definite rules to follow. These are summarized in this tactics box. Part A Your bedroom has a rectangular shape, and you want to measure its area. You use a tape that is precise to 0.001 m and find that the shortest wall in the room is 3.547 m long. The tape, however, is too short to measure the length of the second wall, so you use a second tape, which is longer but only precise to 0.01 m. You measure the second wall to be 4.79 m long. Which of the following numbers is the most precise estimate that you can obtain from your measurements for the area of your bedroom? • View Available Hint(s) O 17.0 m2 O 16.990 m? O 16.99 m? O 16.9 m? O 16.8 m2