Question

a car travels first 30 km with a uniform speed of 60 and then next 30km with uniform speed of 40km calculate the total time of the journey and the average speed of the car​

Answer 1

Answer:-

Given:

A car travels first 30 km with a speed of 60 km/h and next 30 km with a speed of 40 km/h.

That means,

Total Distance = 30 + 30 = 60 km

Time taken to travel first half = Distance covered for the first half / speed of the car

Time taken to travel first half = 30 / 60

→ Time taken to travel first 30 km = (1/2) hours.

Similarly,

Time taken to travel next 30 km = 30 / 40

→ Time taken to travel next 30 km = (3/4) hours.

Total Time of the journey = 1/2 + 3/4 = (2 + 3) / 4

• Total Time of the journey = (5/4) hours

Average speed of the car = Total Distance travelled / total Time taken.

→ Average speed of the car = 60 / (5/4)

→ Average speed of the car = 60 * (4/5)

• Average speed of the car = 48 km/h.

Answer 2

Explanation:

Time = Distance/Speed

t1 = 30/60 = 1/2 hr and t2 = 30/40 = 3/4 hr

Now,

Average speed = Total distance/Total time

Total distance covered = 30 + 30 = 60 km

Total time taken = t1 + t2

= 1/2 + 3/4

= (2 + 3)/4

= 5/4

Therefore,

Average speed = 60/(5/4)

= 60*4/5

= 48 km/hr

Shortcut Method

Average speed = (2 × s1 × s2)/(s1 + s2)

= (2 × 60 × 40)/(60 + 40)

= 4800/100

= 48

Hence, the average speed of the car is 48 km/hr.