SOLUTION: THE COST OF CALCULATORS VARIES DIRECTLY WITH THE NUMBER OF POUNDS BOUGHT. IF 7 CALCULATORS COST $77, WHAT IS THE COST OF 20 CALCULATORS? HELP PLEASE. I AM NOT SURE IF YOU CAN USE A

Question 828303: THE COST OF CALCULATORS VARIES DIRECTLY WITH THE NUMBER OF POUNDS BOUGHT. IF 7 CALCULATORS COST $77, WHAT IS THE COST OF 20 CALCULATORS? HELP PLEASE. I AM NOT SURE IF YOU CAN USE A PROPORTION.
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
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assuming that the weight of calculators is directly proportional to the number of calculators:
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c = Kn
where:
n = number of calculators
c = cost
K = constant of proportionality
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K = c/n
K = 77/7
K = 11
---
c = 11n
c = 11*20
c = $220
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