A truck left 8 hours early than the scheduled time and in order to reach its…

To solve this problem, we can use the relationship between distance, speed, and time. Let the usual speed of the truck be 's' km/hr.

Step-by-Step Calculation
Define the variables:

Distance (d) = 600 km

Usual speed = s

New speed = (s - 20)

Time difference = 8 hours (since the truck left 8 hours early but still arrived on time, it essentially took 8 hours longer to reach the destination).

Set up the equation:
The time taken at the slower speed minus the time taken at the usual speed equals the time difference (8 hours).
(600 / (s - 20)) - (600 / s) = 8

Simplify and solve for 's':
600 * (1 / (s - 20) - 1 / s) = 8
600 * ((s - (s - 20)) / (s * (s - 20))) = 8
600 * (20 / (s^2 - 20s)) = 8
12000 = 8 * (s^2 - 20s)
1500 = s^2 - 20s
s^2 - 20s - 1500 = 0

Factoring the quadratic equation:
(s - 50)(s + 30) = 0

This gives us two possible values for 's': 50 or -30. Since speed cannot be negative, the usual speed must be 50 km/hr.