Standard form
In a nutshell
Standard index form (or standard form) is a convenient way of writing very large or very small numbers.
What does standard form look like?
A number is in standard index form if it is written in the form:
a×10b
Where the number a is always between 1 and 10, and b is a whole number.
Writing a number in standard form
To write a number in standard index form, follow this procedure.
procedure
1.
| Move the decimal point until the number is between 1 and 10. Count how many spaces the decimal point was moved.
|
2.
| This number between 1 and 10 is the value of a.
|
3.
| The number of spaces the decimal point was moved is the value of b. If the decimal point moved to the left, then b is positive. If the decimal point was moved to the right, then b is negative.
|
Example 1
What is 76000 in standard index form?
First, write 76000 as 76000.00 and move the decimal point until the number is between 1 and 10:
7.6000↶↶↶↶00, so a=7.6
The decimal point moved 4 spaces to the left, so b=4.
76000=7.6×104
Example 2
What is 0.0000815 in standard index form?
First, move the decimal point until the number is between 1 and 10:
000008.↷↷↷↷↷15, so a=8.15
The decimal point moved 5 spaces to the right, so b=−5.
0.0000815=8.15×10−5
Multiplying and dividing in standard form
To multiply and divide two numbers in standard form, use your calculator to multiply the numbers. Then, make any adjustments if necessary to make sure the answer is in standard form.
Example 3
What is (1.5×108)×(9×10−3)?
Using the calculator gives:
(1.5×108)×(9×10−3)=1350000
Convert 1350000 into standard form:
1350000=1.35×106
(1.5×108)×(9×10−3)=1.35×106