I'm confused on how to create ratios

Example:
Latoya's Recipe is 9:20
2 1/5 parts cranapple juice
1 4/5 parts lemonade
i know you add to the total, 4
then the lemonade as a whole is 9
but how do you know to get the four to a 20?
when in
Parker's Recipe is 7:12
2 1/2 parts cranapple juice
3 1/2 parts lemonade
you add, 6
then you get 7,
but to get to 12 you instead of multiplying?
how do you know which to do when or just how do get ratios?

Respuesta :

Answer:

Latoya:

cran : lem = 2 1/5 : 1 4/5

= 11/5 : 9/5

= 11 : 9

Lem : total = 9 : 20

Parker:

cran : lem = 2 1/2 : 3 1/2

= 5/2 : 7/2

= 5 : 7

Lem : total = 7 : 12

Step-by-step explanation:

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