Final answer:
Gym-A becomes the cheaper option after more than 8 months of training, based on the monthly and joining fees of both gyms.
Step-by-step explanation:
To determine at what number of months of training gym-A becomes a cheaper option than gym-B, we need to set up an equation to compare the total costs of both gyms over time. The total cost for gym-A can be represented by the equation C_A = 40 + 15m, where C_A is the total cost of gym-A and m is the number of months. Similarly, the total cost for gym-B is C_B = 20m.
To find when gym-A is cheaper than gym-B, we look for the value of m where C_A < C_B:
- Set up the inequality: 40 + 15m < 20m.
- Subtract 15m from both sides to get: 40 < 5m.
- Divide both sides by 5 to solve for m: m > 8.
Therefore, gym-A becomes the cheaper option after more than 8 months of training.