# Carrying out conversions in scientific notation

• Sep 16th 2011, 06:28 AM
m58
Carrying out conversions in scientific notation
I need to convert 12.56 km to ft. I know it's 41297.35 feet, but I'm not sure how to set up the equation.

So far, I have (I know it's not right)...
(12.56 km/1 ft) * (104.6 ft/1 in) * (87.22 in/1 cm) * (34.34 cm/1 km)

Thanks!
• Sep 16th 2011, 01:45 PM
HallsofIvy
Re: Carrying out conversions in scientific notation
Do you understand that "x unit1/unit2" means that a length of 1 "unit 2" is the same as x "unit1"s? "12.56 km/1ft" is wrong- 12.56 kilometers is the total distance, not the number of kilometers in a foot. "104.6 ft/1 in" is incorrect (where did you get 104.6?), there are 12 in in a foot so it would be 1 ft/12 in= 1/12 ft/in= 0.0833 ft/in . "87.22 in/1 cm" is wrong. There are (approximately) 2.5 cm in an inch so 1/2.5 inches per cm or 0.4 in/cm. "34.34 cm/1 km" is wrong. There are 100 cm in a meter and 1000 m in a km so there are 100000 cm in a km so 100000 cm/km.

You should have (12.56 km)(100000 cm/km)(0.4 in/cm)(0.0833 ft/in)
(That doesn't give exactly 41287.35 because there are serious roundoff errors in a calculation like that.)

I really wonder where in the world you got those numbers!
• Sep 16th 2011, 05:35 PM
bjhopper
Re: Carrying out conversions in scientific notation
Hi m38,
All conversions require some basic knowledge of units or reference to conversion tables

1000m = 1 km 1m= 3.281 ft
12.56 km x1000 x3.281 = 41209.4 ft 4.12094x10^4 ft SN