Answer:
Constant of proportionality k = 7/4 if we take the proportionality relationship as ... number of minutes ∝ number of cupcakes Bor
number of minutes = k . (number of cupcakes)
Explanation:
If a variable x is directly proportional to another variable y indicated by
x ∝ y
Then x = k.y where k is the constant of proportionality
Letting x be the number of cupcakes and y the number of minutes
number of cupcakes = k . (number of minutes)
k = (number of minutes) / (number of cupcakes )
Here k, the constant of proportionality tells you how many many minutes it takes to ice 1 cupcake
For 40 cupcakes it takes 70 minutes. So k = 70/40 = 7/4
For 28 cupcakes it takes 49 minutes so for 1 cupcake it takes 49/28 = 7/4 so again that is the constant of proportionality
k = 7/4 given that number of minutes ∝ number of cupcakes
=> number of minutes = k. number of cupcakes
Note if we had x = number of cupcakes and y = number of minutes then k = 4/7 which is the number of cupcakes that can be iced in 1 minute
So one has to be careful to state what is proportional to what