AlgebraMediumBill with a charge above an allowance
Algebra practice question
A phone plan costs $18 per month and includes 200 text messages; each message beyond 200 costs $0.10. A customer's bill for one month was $25.40. How many text messages did the customer send that month?
Answer: 274
Let t be the number of messages: 18 + 0.10(t − 200) = 25.40 → 0.10(t − 200) = 7.40 → t − 200 = 74 → t = 274.
Common wrong answers
- If you answered 74
- 74 is the number of messages beyond the allowance, not the total.
- If you answered 126
- 126 comes from 200 − 74, subtracting instead of adding.
- If you answered 254
- 254 comes from 25.40 ÷ 0.10, ignoring the $18 base charge and the allowance.
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