Question

A man decides to give his son 1,000 L.L. for every math exercise solved properly to encourage him to study mathematics but takes back 500 L.L. if the solution is wrong. After 30 exercises, each has given and received the same amount. How many exercises did the son solve properly?

Answer 1

The son solved 10 exercises properly.

Step-by-step explanation:

To solve this problem, we can set up an equation. Let's say the son solved x exercises properly. According to the information given, he receives 1,000 L.L. for each exercise solved properly, so he receives 1,000x L.L. from his father. However, he also takes back 500 L.L. for each exercise solved incorrectly, so he takes back 500 * (30 - x) L.L. from his son.

Since the son received and took back the same amount, we can set up the equation 1,000x = 500 * (30 - x). Solving this equation, we find that 1,000x = 15,000 - 500x. Combining like terms, we get 1,500x = 15,000. Dividing both sides by 1,500, we find that x = 10.

Therefore, the son solved 10 exercises properly.