direct variation 2.4. big idea… 5280ft=1mile. there will always be the same number of feet in a...
TRANSCRIPT
Direct Variation2.4
Big idea…
• 5280ft=1mile. There will always be the same number of feet in a mile, so they are “directly proportional”
Definitions
• Direct Variation: When two things are related by a constant ratio
• Equation:
• The numbers x and y and directly proportional, and k is called the constant of variation.
𝑦=𝑘𝑥
Why is it called DIRECT?
• If x or y increases, so does the other.• If x or y decreases, so does the other.
• They move together in unison.
Example 1
1. Find y if x=3.
2. Find x if y=27.
Example 2
• Find y if x=11
• Find x if y=29
Example 3: You try!
• Find y if x=4
• Find x if y=120
Example 4
• What is the first step in solving for x?
Example 5
Your job pays you $9.50 an hour. 1. Define variables (x and y)
2. Write a direct variation equation.
3. How much will you make if you work 8 hours?
4. How many hours did you work if you make $114?
You try!
You drive at a constant speed of 35 mph.1. Define variables (x and y)
2. Write a direct variation equation.
3. How far will you go if you drive for 4 hours?
4. If you travel 175 miles, how long did you drive?
Homework
• 2.4: problems 3,4,5.