Converting from m to cm or mm.
"Centi" means 0.01 or
1
100
You know, cent is 0.01 dollars.
So 1 cm = 0.01m
100 cm = 1m
Another way to write that is
(like 100 cents = 1 dollar)
1
"Milli" means 0.001 or
1000
So 1 mm = 0.001m
Another way to write that is
1000 mm = 1m
Convert 0.15m to cm as follows:
0.15m  100cm   15cm
 1m 
Note the m cancels
Convert 0.00432m to cm
0.00432m  100cm   0.432cm
 1m 
Convert 3.2m to cm
3.2m  100cm   320cm
 1m 
Convert 0.0235m to mm
0.0235m  1000mm   23.5mm

1m

Convert 8.2 x 10-4m to mm.
8.2 x10
4
 1000mm 
1
m 
  8.2 x10 mm  0.82mm
1
m


Exercises:
Try these exercises. Check your answers against those given at the bottom.
1.
Convert 7.09m to cm
2.
Convert 5.02 x 10-5m to mm
3.
Convert 0.023m to cm
4.
Convert 0.00156m to mm
5.
Convert 0.6503m to cm
6.
Convert 1.21m to mm
7.
Convert 7.39 x 10-7m to mm
8.
Convert 0.0802m to mm
9.
Convert 4.506 x 10-4m to cm
10.
Convert 9.21 x 10-2m to cm
Answers:
1.
2.
3.
4.
5.
709cm
5.2 x 10-2mm or 0.052mm
2.3cm
1.56mm
65.03cm
6.
7.
8.
9.
10.
1210mm
7.39 x 10-4 mm or 0.000739mm
80.2 mm
4.506 x 10-2 cm or 0.04506cm
9.21 cm
Practice Estimating Sizes – Part 1
Keep three approximate sizes in mind: 1m, 1cm, 1mm.
Write down (on this sheet) what you decided to use from the class exercise.
Common Object/Distance
Length
1m
1 cm
1 mm
My Choice
Floor to my hip bone
Thickness of pinky
Diameter of wire in a paper clip
Your Choice
To estimate sizes, compare to one of the above three objects.
Example 1: What object is 2.1m in size?
I'd compare to 1m. 2.1m is a little over twice the distance from floor to my hip
bone. That's over twice as tall as I am. So I'd estimate 2.1m as the height of a door
or the height of a 6 ft person.
Example 2: What object is 4.3cm in size?
That's a bit more than 4 pinky thicknesses so maybe the length a big grape golf ball.
(We're approximating!)
Example 3: What object is 0.52mm in size?
This is about ½ a mm so ½ the diameter of the wire in a paper clip. That would be
enough. You could also say the thickness of a pin.
Example 4: What object is about 7.2m in size?
I'd pace this off. A giant step for me is about 1m.
So 7 giant steps later I can see how big this is. That's about ¾ of the way across
our classroom (C 256). Maybe the length of a big car.
Exercises:
Try these exercises. After you estimate, check your answers against those given at the
bottom.
1.
What object is about 4.6m in size?
2.
What object is about 0.63m in size?
3.
What object is about 12.2m in size?
4.
What object is about 0.9m in size?
5.
What object is about 8.2m in size?
6.
What object is about 0.92m in size?
7.
What object is about 0.38m in size?
8.
What object is about 16.2m in size?
9.
What object is about 1.5mm in size?
10.
What object is about 12.4mm in size?
11.
What object is about 0.2mm in size?
12.
What object is about 3.6mm in size?
Answers (Since we are estimating, answers will vary)
1.
2.
3.
4.
5.
6.
Length of small car or half a first down.
Desk height.
Width of classroom.
Hip height or length of yardstick.
Width of calculator.
Pencil width.
7.
8.
9.
10.
11.
12.
Diameter of small pea.
Length of calculator.
Width of pencil lead.
Diameter of large pea.
Phew, small! Tip of pin.
Diameter of small pea.