The relative change can be calculated using the formula for percentage change:

$\text{Relative change} = \frac{\text{New value} - \text{Old value}}{\text{Old value}} \times 100$

Here:

• The old value is 40 miles per hour (normal speed limit).
• The new value is 25 miles per hour (school hours speed limit).

Substituting the values:

$\text{Relative change} = \frac{25 - 40}{40} \times 100 = \frac{-15}{40} \times 100 = -37.5\%$

So, the relative change is $-37.5\%$.

Would you like more details or have any questions?

Here are five questions that expand on this:

1. What is the difference between absolute and relative change?
2. How can you interpret a negative relative change in real-world situations?
3. Can relative change ever exceed 100%? In what scenarios?
4. How would the relative change differ if the initial speed were 60 mph instead of 40 mph?
5. How do you calculate relative change in scenarios where the new value is greater than the old value?

Tip: When dealing with percentage decreases, always check if the change is expressed as a positive or negative value to avoid confusion.