A proportion is a statement of equality of two or more ratios
Remember: A ratio is a comparison of two numbers by division
Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students?
And the answer is…….Chicken Fingers and Students
Chicken Fingers Students---------------------- OR -------------Students Chicken Fingers
As a Ratio this looks like…..
Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students?
And the Answer is….Meters and Seconds
Meters Seconds---------- OR ------------Seconds Meters
As a Ratio this looks like…..
And the answer is….Miles and Hours
As a Ratio this looks like…..
Miles Hours--------- OR --------Hours Miles
Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students?
First Step:Chicken Fingers Students---------------------- OR --------------Students Chicken Fingers
Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students?
And the answer is….
Chicken Fingers 48 X-------------------- ------ AND ----- Students 20 30
FYI Can you flip the ratio so that students
were on top and chicken fingers were on bottom?
YES! If you flip the ratios so that students are on top and chicken fingers were on bottom you must just be careful to do this for all your ratios. Therefore then 48/20 would change to 20/48 and
x/30 would become 30/x.
Chicken Fingers 48 X-------------------- ---- AND ----Students 20 30
OR Students 20
30----------- ------ AND ------- Chicken Fingers 48 X
Jane ran 100 meters in 15 seconds. How long did she take to run 1 meter?
Meters Seconds---------- OR ------------Seconds Meters
First Step:
Jane ran 100 meters in 15 seconds. How long did she take to run 1 meter?
And the answer is…..Meters 100 1--------- ------ AND -------Seconds 15 X
1. Chicken Fingers ----------------------
Students
2. 48 X---- AND ----20 30
3. 48 X ----- = --- 20 30
Suppose it takes 48 chicken fingers to feed Mr. Young’s 4th grade class of 20 students. How many chicken fingers would be needed for 30 students?
And the answer is……
1. Meters ---------- Seconds
2. Meters 100 1--------- ------ AND -------Seconds 15 X
3. 100 1 ------ = ------- 15 X
And the answer is…..
1. Miles ------- Hours2. Miles 125 X ------- ------ AND
------- Hours 3 52
3. 125 X ------ = ------- 3 5
Cross Multiply means that you MULTIPLY DIAGONALLY across…..
…….Like crisscross apple sauce when you are sitting
And then…..Set the two products (ANSWERS) EQUAL to each
other
4X = 63
And the answer is…(100)(X)= (15)(1)100X= 15X= 15/100X= .15 It took Jane .15 seconds to run a meter
100 1 ------ = ------- 15 X
(125)(5) = (3)(X)625 = 3X625/3=XX= 208.3In 5 hours the car would have traveled 208.3
miles.
125 X ------ = ------- 3 5
Mix 3 liters of water with 4 lemons to make lemonade. How many liters of water are mixed with 8 lemons.
1. What are you comparing?Liters and LemonsLiters Lemons------- OR -------Lemons Liters
Mix 3 liters of water with 4 lemons to make lemonade. How many liters of water are mixed with 8 lemons.
2. What are your two ratios? Liters 3 X --------- ------ AND ------
Lemons 4 8
3. Set the two ratios equal to each other 3 X ---- = -----
4 8
Mix 3 liters of water with 4 lemons to make lemonade. How many liters of water are mixed with 8 lemons.
Mix 3 liters of water with 4 lemons to make lemonade. How many liters of water are mixed with 8 lemons.
4. Cross Multiply 3 X---- = ----- (4)(X) = (3)(8) 4 8
5. Solve4X= 24X= 24/4X= 6You will need 6 liters of water for 8 lemons.