Exact Numbers What make a number exact?. Exact Numbers There are three different ways to know if a...
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Transcript of Exact Numbers What make a number exact?. Exact Numbers There are three different ways to know if a...
Exact Numbers
What make a number exact?
Exact Numbers
There are three different ways to know if a number is exact.
1. Numbers from counting things.2. Numbers used in unit conversions.3. Numbers in formulas.
Counting things
• When you count a whole number of things, you have an exact number.– When you count things like pennies you
have an exact number of pennies. – If you are counting pies and someone ate
half of one. You no longer have an exact number of pies.
Conversion of units
• When you use a conversion factor to convert from one unit to another, these are exact numbers.
If you have 2000 mL of milk and you know there are 1000mL in a 1L.
2000 mL X 1 L = 2L
1000 mL
Conversion factor exact numbers
Numbers in formulas
• When you use rational numbers in a formula , you have exact numbers
• Area of a triangle = ½bh the ½ is exact.
• Circumference of a square = 4s the 4 is exact
Exceptions in formulas
• When the formula includes an irrational number, the irrational number is not exact.
• circumference of a circle = 2πr the 2 is exact
π is not exact
Summary of Exact Numbers
• When you count a whole number of things, you have an exact number.
• When you use a conversion factor, these are exact numbers.
• When you use rational numbers in a formula , you have exact numbers.