Q1. Ravi travels 60km in 1 hour and 60km in 2 hours. What is his average speed?
✔ Total distance is 120km. Total time is 3 hours. 120 divided by 3 equals 40.
Q2. Siti travels from Tampines MRT to a hawker centre. Which method finds average speed?
✔ Average speed is always calculated using total distance divided by total time.
Q3. Wei Ming calculates average speed as (60 + 30) / 2. What is his mistake?
✔ Averaging speeds ignores that more time was spent at the slower speed.
Show transcript
[Slide 1] Understanding Average Speed
Hello students! Today we learn average speed for PSLE. Remember, it is not just averaging two numbers. We must look at the whole journey carefully.
[Slide 2] The Golden Rule
The rule is simple but tricky. You divide the total distance by the total time taken. Never add the speeds and divide by two.
[Slide 3] Ravi's Journey to Tampines
Let us look at Ravi travelling to Tampines. First, he goes sixty kilometres to the MRT station. Then he travels another sixty kilometres to eat.
[Slide 4] Calculating with Bar Model
Using the bar model, we combine the distance bars. We also add the time blocks together. Finally, divide the total distance by total time.
[Slide 5] Avoiding Common Mistakes
Many students average the speeds like forty five kilometres per hour. This is wrong because time spent differs. Stick to the total distance formula always.
[Slide 6] PSLE Recap for Speed
To recap, find the total distance and time. Then divide to get the average speed. Practice this for your PSLE exam soon.