The product of 5 and 2.5 is 12.5, but this number implies a range from 12.4 to 12.6 cm 2 . Clearly, the actual area could be outside the range of 12.4 to 12.6 cm 2 . 12.5 can rounded to 13. The only instruments available are your odometer, and your wrist watch. Your stopwatch indicates that 159.5 seconds have elapsed.
Average speed equals distance traveled divided by elapsed time.
Some numbers have an unlimited number of significant figures. These numbers are called exact numbers . These numbers are numbers about which one is absolutely certain. Every several years the United States attempts to count the number of people in the country. An Example Three measurements were made of the length of my office.