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How do u convert between the metric system and the english system

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7 Answers

For quick conversions you can use google or some other unit converter. Otherwise, if you need to show work or if you need practice, use dimensional analysis. In other words, multiply your number 4.92 inches times the converting factors needed. You can go step by step, converting from inches to centimeters and then centimeters to millimeters. 
 
the converting factors are as follows:
 
    1 inch = 2.54 cm,   or      2.54 cm/1 inch = 1,       or  1 inch/2.54 cm = 1
    1 cm = 100 mm, or          1 cm/100mm = 1,         or  100mm/1cm = 1


you can use conversion factors to convert either way. 
Line up your numbers and units in your dimensional analysis to make sure you dont mix up the units.
 
 
ie:
 
         4.92 inches  x   2.54 cm  =  12.496 cm     x  100 mm  =   1249.6 mm  = 1250 mm 
                                  1 inch                                  1 cm                         
 
 
note that I bolded the significant figures. Remember, conversion factors are exact; in this case, you start off with three sig figs so your final converted units should also be 3 sig figs. You should round your answer only at the end of you calculations to prevent error propagation.  
 

Comments

Dimensional analysis is very safe way of converting as long as you keep everything straight, by the way your final answer should be 1250 mm or 1.25 x 103 mm.
 
Jeff
Thanks for the correction, I mistyped the final answer. it should be 1250 mm or 1.25 x103mm as you said

Comment

1 inch = 25.4 millimeter
4.92 inches = 25.4 * 4.92 millimeter = 124.968 millimeter
Thus 4.92 in = 124.968 mm
Let me add that conversion tables should be in your textbook.
Metric to English
 
Metric                                English
Centimeters (cm) x .39 =  inches
 
Meters (m) x 3.3 =            feet
 
Meters (m) x 1.1 =           yards  
 
Kilometers (km) x .6 =     miles
 
Sq. centimeters (cm2) x .2 = square inches
 
Square meters (m2) x 10.8 = square feet
 
Square meters (m2) x 1.2 = square yards
 
Hectares (ha) x 2.5 =       acres
 
Cubic meters (m3) x 35.3 = cubic feet
 
Liters (l) x 1.1 =             quarts (lq)
 
Cubic meters (m3) x 284.2 = gallons
 
Grams (g) x .04 =           ounces (avdp)
 
Kilograms (kg) x 2.2 =   pounds (avdp)
 
Kilowatts (kW) x 1.3 =  horsepower
You start with what ever you know.5.00 meters 
 
5.00 m x ______in    the equivalent for m to inches is 0.0254 m = 1.in
                    m
 
5.00 m x  1in/ 0.0254 m  =197. inches
 
this is equivalent to 2.54 cm = 1 in
or 1 m = 39.37 in
remember if you keep significant digits the same as the measured number.
The number you start with units will match the denominator units; and the equivalent units in the numerator or on top. 
1 L = 1.057 qt= 1000 cubic cm
The easiest conversion to remember in this case is 2.54 cm = 1 in
When converting units make sure that the units cancel
4.92in x (2.54cm/1in) x (10mm/1cm) = 124.968mm
inches cancel and cm cancel
 
Hi Angela;
This is the easiest technique I know of...
Please memorize...
1 inch = 2.54 centimeters or 25.4 mm
So...
25.4 mm/1 inch = ? mm/4.92 inches
Multiply both sides by 4.92 inches...
(4.92 inches) (25.4 mm/1 inch)=(4.92 inches)(? mm/4.92 inches)
Cancel out words...
(4.92 inches) (25.4 mm/1 inch)=(4.92 inches)(? mm/4.92 inches)
Proceed to cancel out words...
(4.92) (25.4 mm/1)=(4.92 inches)(? mm/4.92 inches)
Cancel out numbers...
(4.92) (25.4 mm/1)=(4.92)(? mm/4.92)
(4.92)(25.4 mm)=? mm
=124.968 mm