1. The area of a circle is found to be 2.4 cm2. What is the area in m2?
QUESTION:
The area of a circle is found to be 2.4 cm2. What is the area in m2?
A. 2.4x102 m2, B. 2.5x10-2 m2,
C. 2.4x10-4 m2, D. 5.8x104 m2
The area of a circle is found to be 2.4 cm2. What is the area in m2?
PAUSE CLICK CONTINUED ON NEXT SLIDE

2. The area of a circle is found to be 2.4 cm2. What is the area in m2?
QUESTION:
The area of a circle is found to be 2.4 cm2. What is the area in m2?
A. 2.4x102 m2, B. 2.4x10-2 m2,
C. 2.4x10-4 m2, D. 5.8x104 m2
10-2 m
10-2 m
2.4 cm cm x x
= 2.4x10-4 m2
1 cm
1 cm
In this problem, we are asked to change from square centimeters to square meters.
By now you should know that the prefix centi means 10-2.
This means that 1 centimeter is meters.
So the possible conversion factors that we can use are
HIGHLIGHT 1 cm/10-2 m
1 centimeter over 10-2 meters,... or
HIGHLIGHT 10-2 g / 1 cm
10-2 meters over 1 centimeter
Let’s see which ones we need to use.
First, we write the known amount centimeters squared
CLICK Note that when you square something, you multiply it by itself. So, centimeter squared is centimeter time centimeter.
HIGHLIGHT cm cm
Since we want to replace centimeter by meter, we use the conversion factor that will allow
us to cancel centimeter.. Therefore , we use this conversion factor....
HIGHLIGHT 10-2 m / 1 cm
We multiply our known amount...
CLICK
by 10-2 meter
over
CLICK 1 centimeter
This cancels out one of the centimeter units.
SHOW CANCELLATION OF cm units
To cancel the other centimeter unit, we multiply by the same conversion factor one more time.
CLICK CLICK
Now we can cancel the other centimeter unit.
This gives us an answer of 2.4x10-4 meters squared.
We need to express our answer to two significant digits.
since our original quantity has 2 significant digits.
Therefore, the correct answer is C.
CLICK Here’s a more compact way of doing the conversion...
We multiply our original amount
HIGHLIGHT 2.4 cm2
by the square of the centimeter-to-meter conversion factor.
HIGHLIGHT conversion factor
PAUSE
PAUSE END RECORDING
1 cm
10-2 m
10-2 m
1 cm

3. Video ID: 1A-5-6 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08