Final answer:
If you travel at 4/5th of your usual speed and take 40 minutes longer to reach your destination, your usual time is 200 minutes.
Step-by-step explanation:
Let's assume your usual speed is S and the time taken to reach your destination at this speed is T. According to the given information, if you travel at 4/5th of your usual speed, your new speed would be 4/5 * S. The new time taken to reach your destination would be T + 40 minutes.
Using the formula time = distance / speed, we can equate the two times:
T = (distance traveled) / S
T + 40 = (distance traveled) / (4/5 * S)
Cross multiplying, we get:
5T = 4(T + 40)
Solving this equation, we find T = 200 minutes. Therefore, your usual time to reach your destination is 200 minutes.