Factor-Label Method (of conversion)

• The factor-label method was developed to keep track of units in multi-step conversion problems

• Factor-label method is a method for solving problems.

• It is a neat and organized method that can be used in science, math, shopping, building, cooking and many other situations.

• In life you will need to be able to switch back and forth between different units.

• For example- a video may be listed as 101 minutes long. You want to know how long the movie is in hours, to find out you need to do a factor label problem.

• To solve this problem we are going to learn a generic set-up and use it to solve EVERY problem for the rest of the year.

What you = what you know x the fractions you want to find need to get your answer

For our video problem…

• What you want to find = hours

• What you know = the movie is 101 minutes

• The fractions you need= 1 hour = 60 minutes

The set up would look like…

# hours = 101 min x =1 hour60 min 1.68 hours

Make sure…

• Units cancel out-----

• This means what ever you start with is ‘on top’ and you alternate units top and bottom so they cancel out.

A B C DA B CX X X = D

Make sure…

• You box your answer.

• I won’t know what your answer is if I cannot find it!

Lets try another one!

• Many of the problems will involve more than one step, so lets take the video problem a little further.

• The video is 101 minutes long, how many days long is it?

• What we want to find = days

• What we know = the movie is 101 minutes

• Fractions we need = 1 hour = 60 minutes• 1 day = 24 hours

# days = 101 min 1 hour 1 day 60 min 24 hr

X X = 0.0701 days

If I am driving 2 km/sec how fast am I going in miles / hour?

2 Km 1000 m 1 mi 60 sec 60 min 1 sec 1 Km 1600 m 1min 1 hrX X X X =

4500 mph

Try one or two with a partner!