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Significant digits, also known as significant figures, measure the overall relative accuracy of a value. They represent the number of digits that are considered meaningful in a measurement.
Significant digits can be a bit confusing if you're not sure which are deemed significant and which are not. Here's a look at some rules for identifying significant digits in a number:
Let's look at numbers with similar digits that have a different number of significant digits:
0.054 has 2 significant digits
0.504 has 3 significant digits
504.0 has 4 significant digits
504.00 has 5 significant digits
5004.00 has 6 significant digits
0.000834 has 3 significant digits
0.008034 has 4 significant digits
0.080034 has 5 significant digits
0.803400 has 6 significant digits
8.003400 has 7 significant digits
Rounding is a way to eliminate some digits you don't need in a number while maintaining a level of accuracy. The person rounding a number typically decides how many significant digits they'd like to keep based on their measurement requirements. Before looking at how to round significant digits, let's look at some important terms related to rounding:
a. How many significant digits are in the number 0.172693?
Answer: 6
b. How many significant digits are in the number 89.300?
Answer: 5
c. How many significant digits are in the number 0.000235?
Answer: 3
d. How many significant digits are in the number 745300?
Answer: 4 (unless one or both of the zeros are needed for the measurement)
e. What is 12.7803 when rounded to 3 significant digits?
Answer: 12.8
f. What is 6392.81 when rounded to 5 significant digits?
Answer: 6392.8
g. What is 1.338 when rounded to 2 significant digits?
Answer: 1.3
h. What is 788.66 when rounded to 4 significant digits?
Answer: 788.7
ACCUPLACER Arithmetic Flashcards
Basic Arithmetic Diagnostic Tests
Understanding significant digits is not always easy because there are so many rules to remember. It can become even more complicated when determining how to round significant digits. If your student is having trouble grasping the concept of significant digits or would like help with related concepts, an assignment, or test preparations, they could benefit from tutoring sessions. Get valuable information about the perks of working alongside a tutor by reaching out to the Educational Directors at Varsity Tutors.