16Hit1600
AlgebraHardInequality from a rate comparison

Algebra practice question

Plan A charges $0.10 per text message with no monthly fee. Plan B charges a $6 monthly fee plus $0.04 per text. For how many texts t per month is Plan B cheaper than Plan A?

  1. A. t > 100Correct
  2. B. t < 100
  3. C. t > 60
  4. D. t > 150

Answer: A. t > 100

B cheaper: 6 + 0.04t < 0.10t, so 6 < 0.06t and t > 100.

Why the other answers are wrong

B. t < 100
For t < 100, Plan A is cheaper.
C. t > 60
60 is 6/0.10, comparing the fee to A's rate alone.
D. t > 150
150 is 6/0.04, comparing the fee to B's rate alone.

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