Analyze Mr. Johnson's work and identify his
mistake.
Mr. Johnson is also comparing the two mobile
phone data plans. Talk First charges $20 plus $5
per GB of data while Mobile Plus charges $30
plus S3 per GB of data At what amount of GB use
will the cost of the two data plans be the same?
Mr. Johnson wrote this equation for the scenario.
1. d = amount of data used (GB)
2. Talk First = Mobile Plus
3.200 + 5 = 300 + 3
In step 1. his variable should be c.
representing company.
In step 2 his translated equation should be
Talk First + Mobile Plus = Total
Money
In step 3 he multiplied the variable by the
base monthly cost instead of by the
cost per GB