You drive your car at a speed 40km/h for 1 hour, then slow down to 30km/h for the next 20km. How far did you drive, and what was your average speed?
To find the total distance you drove, you need to calculate the distance traveled at each speed and then add them together.
First, calculate the distance traveled at 40 km/h. You drove at this speed for 1 hour, so the distance can be found using the formula: distance = speed × time. Therefore, distance = 40 km/h × 1 hour = 40 km.
Next, calculate the distance traveled at 30 km/h. This time, you need to convert the speed from kilometers per hour to kilometers per minute since you drove for 20 km. The formula to convert speed from km/h to km/min is to divide it by 60. Therefore, the speed in km/min is 30 km/h / 60 = 0.5 km/min. The time traveled at this speed is 20 km / 0.5 km/min = 40 minutes.
Now that you know the time and speed, you can find the distance using the formula: distance = speed × time. Therefore, distance = 0.5 km/min × 40 minutes = 20 km.
Adding up the distances traveled at each speed, you get 40 km + 20 km = 60 km.
To find the average speed, you need to calculate the total time traveled and divide the total distance by the total time. You drove for 1 hour at 40 km/h and for 40 minutes at 30 km/h. To calculate the total time, convert the 40 minutes to hours. There are 60 minutes in an hour, so 40 minutes is 40/60 = 2/3 hours.
The total time traveled is 1 hour + 2/3 hours = 5/3 hours.
Finally, divide the total distance (60 km) by the total time (5/3 hours) to find the average speed.
Therefore, the average speed is 60 km / (5/3) hours = 36 km/h.