Exact Numbers
Obtained when you count objects
2 soccer balls
1 watch
4 pizzas
Obtained from a defined conversion factors
1 foot = 12 inches
1 meters = 100 cm
Not obtained with measuring tools
 Do not limit the # of sig figs in the answer.
Learning Check
A. Exact numbers are
1. measured values
2. count values
3. defined conversion factors
B. Measured numbers are obtained by
(from)
1. using a measuring tool
2. counting
3. defined conversion factors
Learning Check
Classify each of the following as an exact (1)
or a measured (2) number.
A.___Gold
melts at 1064°C
2
B.___1
1 yard = 3 feet
C.___A
red blood cell with diameter 6 x 10-4 cm
2
D.___There
were 6 hats on the shelf
1
E.___A
can of soda contains 355 mL of soda
2