Problem
Some of the most common (and most dangerous) examples of simple interest are short-term payday loans, which some lenders also call "cash advances". (This is not to be confused with a cash advance on a credit card.) Let's say that you're going to get paid in ten days, and you need some cash for a car repair now. A payday lender might lend you $\$ 700$ now, and you'll be asked to pay them back when your paycheck comes. Of course, you'll have to pay interest. The median fee charged by these types of lenders is $\$ 25$ per every $\$ 200$ borrowed. How much would you have to pay back in ten days? The amount of money you'd have to pay back is $\$ \square$.
Solution
Step 1 ：Calculate the number of times the median fee is charged for a $700 loan: \(\frac{700}{200} = 3.5\)
Step 2 ：Calculate the total interest: \(3.5 \times 25 = 87.50\)
Step 3 ：Calculate the total amount to be paid back: \(700 + 87.50 = 787.50\)
Step 4 ：\boxed{787.50}
