Question

Some part of a journey of 555 km was completed by a car with speed 60 km/h. Then the speed is increased by 15 km/h and the journey is completed. If it takes 8 hours to reach, find the time taken and distance covered by 60 km/h speed.

Answer 1

Initial speed = 60 km/h
When the speed is increased by 15 km/h, then the new speed will be 75 km/h.
Let the duration of time of the journey covered at a speed of 60 km/h be x hours and that of the journey at a speed of 75 km/h be y hours.
According to the question, we have:
x + y = 8 ...(1)
Also, 60x + 75y = 555
$\Rightarrow$15(4x + 5y) = 555
⇒ 4x + 5y = 37 ...(2)
Multiplying equation (1) by 4, we get:
4x + 4y = 32 ...(3)
Subtracting equation (3) from equation (2), we get:
4x + 5y = 37
4x + 4y = 32
---------------------------
y = 5
Substituting the value of y in equation (1), we get:
x + 5 = 8
⇒ x = 3

Now, time taken at a speed of 60 km/h = 3 h
∴ Distance covered at a speed of 60 km/h = $60\times 3=180\mathrm{km}$