To find the break-even point, we need to set up equations to represent the total cost for each option based on the number of visits.
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Cost for single visits: \[ \text{Cost}_{\text{single}} = 28 \cdot x \] where \( x \) is the number of visits.
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Cost for the monthly membership: \[ \text{Cost}_{\text{membership}} = 90 + 15 \cdot x \]
To find the break-even point, we set the two cost equations equal to each other: \[ 28x = 90 + 15x \]
Now, we will solve for \( x \):
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Subtract \( 15x \) from both sides: \[ 28x - 15x = 90 \] \[ 13x = 90 \]
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Divide both sides by 13: \[ x = \frac{90}{13} \approx 6.92 \]
Since the number of visits must be a whole number, we can round \( 6.92 \) to either 6 or 7 visits.
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Calculating costs for 6 visits:
- Single visits: \( 28 \cdot 6 = 168 \)
- Membership: \( 90 + 15 \cdot 6 = 90 + 90 = 180 \)
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Calculating costs for 7 visits:
- Single visits: \( 28 \cdot 7 = 196 \)
- Membership: \( 90 + 15 \cdot 7 = 90 + 105 = 195 \)
Thus, at 6 visits, the membership is more expensive, while at 7 visits, the membership becomes less expensive.
Therefore, the approximate break-even point is at 7 visits. Beyond this point, the monthly membership becomes the more cost-effective option.