Problem 2. When multiplying two numbers, the student replaced the unit digit 4 of the first number with 1. Thus, he got 525 instead of 600. What numbers did he multiply?
Solution. From the condition, we have that when the first number is reduced by $4-1=3$, then the product has decreased by $600-525=75$. This means that the number is $75: 3=25$. The second number will be obtained as $600: 25=24$. Therefore, the student multiplied the numbers 25 and 24.