Chapter 1 - Introduction to Physics - Problems and Conceptual Exercises - Page 15: 13

a) 3.14 b) 3.1416 c) 3.141593

The first several digits of $\pi$ are known to be $\pi$ = 3.14159265358979... While rounding off the digits, if the number after the last place has a number greater than or equal to 5, the last digit is increased by 1 unit, but if the digit is less than five, the face value of the digit will not change. a) 3 significant digits will include only 3 digits. It will be rounded off as 3.14. The number after 4 is less than 5, and, therefore, it will be rounded off to 3.14 not 3.15. b)5 significant digits 3.1416 Because the number after 5 was 9, the value of the last digit was increased by 1. c)7 significant digits 3.141593 Because the number after 2 was 6, the value of the last digit was increased by 1.