AlgebraMediumJoining fee from two totals
Algebra practice question
A gym membership costs a one-time joining fee plus a fixed amount each month. After 2 months a member has paid $90 in total, and after 5 months $180 in total. What is the joining fee, in dollars?
Answer: 30
Three extra months cost 180 − 90 = $90, so the monthly amount is $30. After 2 months: fee + 2(30) = 90, so the fee is $30.
Common wrong answers
- If you answered 36
- 36 is 180/5, again ignoring the fee.
- If you answered 45
- 45 is 90/2, treating the whole first-two-months total as monthly charges with no fee.
- If you answered 60
- 60 is 90 − 30, subtracting the monthly amount only once; two months had been paid.
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