A car travels a total distance of 400 km. It covers the first half of the distance at a speed 40 km/h and the second half of the distance at speed v. If the average speed is 48 km/h, then the value of v in km/h is 60 km/h87 km/h79 km/h94 km/h

To find the value of v, we can use the formula for average speed, which is total distance divided by total time.

Let's first calculate the time taken to cover the first half of the distance. The distance covered in the first half is 400 km divided by 2, which is 200 km. The speed for the first half is given as 40 km/h, so the time taken for the first half is 200 km divided by 40 km/h, which is 5 hours.

Now, let's calculate the time taken to cover the second half of the distance. The distance covered in the second half is also 200 km. We can use the formula for average speed to find the time taken. The average speed is given as 48 km/h, so the time taken for the second half is 200 km divided by 48 km/h, which is approximately 4.17 hours.

The total time taken to cover the entire distance is the sum of the time taken for the first half and the time taken for the second half. So, the total time is 5 hours + 4.17 hours, which is approximately 9.17 hours.

Now, we can use the formula for average speed to find the value of v. The average speed is given as 48 km/h, and the total distance is 400 km. So, we can rearrange the formula to solve for v:

average speed = total distance / total time

48 km/h = 400 km / 9.17 hours

To solve for v, we can rearrange the formula as:

v = (total distance - (speed for first half * time for first half)) / time for second half

v = (400 km - (40 km/h * 5 hours)) / 4.17 hours

v = (400 km - 200 km) / 4.17 hours

v = 200 km / 4.17 hours

v ≈ 47.99 km/h

Therefore, the value of v is approximately 48 km/h.