Calculating Rates

1
Calculating Rates
2
Speeds

• Speeds are often described as rates.
• Ex MPH miles per hour
• MPS meters per second
• In all the following slides we will use d for
  distance, t for time and r for rate.

3
How far?

• If you traveled at 30 MPH for 3 hours, how far
  would you go?
• If you traveled for 10 hours at 60 MPH, how far
  would you go?
• What operation did you use to figure the distance?

4
Formula (or an equation)

• If 90 miles 30MPH 3 hours
• And
• 600 miles 10 hours 60 MPH
• Then
• Distance rate time or
• D rt

5
Finding Rate

• If you go 60 miles in one hour, what is your
  rate?
• If you go 60 miles in 2 hours, what is your rate?

6
Formula for Rate

• If 60 MPH 60 miles/ 1 hour
• and
• 30 MPH 60 miles/ 2 hours
• What is a formula for figuring rate?

r d/t rate distance divided by time
7
Formula for time

• How long will it take you to go 90 miles at 30
  MPH?
• How long will it take to go 600 mile at 60 MPH?
• Which operation did you use?

8
Formula for Time

• 3 hrs 90 miles divided by 30 MPH
• 10 hrs 600 miles divided by 60 MPH

Time Distance / rate t d/r
9
Which is the faster rate?

• 35 miles in 15 minutes
• Or
• 76 miles in 30 minutes
• rd/t

rd/t r35/15 r2.3 mph rd/t r76/30 r2.5 mph
10
Which is farther?

• d rt
• 17 mph for 17 minutes
• Or
• 11 mph for 22 minutes

d rt d 17(17) d 289 miles Or d rt d
11 22 d 242 miles
11
Which takes longest?

• td/r
• Go 40 miles at 22MPH
• Or
• Go 60 miles at 28 mph

t d/r t 40/22 t 1.8 hours t d/r t 60/28 t
2.1 hours