(Viva Voce) Chap 9 Exercise 9 Question 2

a) average speed of car X=60km/45min

b)average speed of car Y=72km/80min(1h20min=80min)
9/10km x60=54km

c)ratio of average speed of car X to car Y


  1. accuracy: 2
    understanding: 2
    explanation: 3
    mathematical terms: 1

  2. Accuracy of answer = 2
    Mathematical terms = 1
    Explanation of working/solution = 3
    Presentation = 1
    Reason(Presentation):The words and numbers in the video was not clear enough for me to read what you were pointing to.

  3. accuracy of answer[2]
    mathematical term[1]
    explanation of working/solution[3]
    understanding of concept[2]
    presentation[2]( unable to see the working on the paper]

  4. 1. You mentioned what's required to find at the beginning so that we know why you highlighted the formula. Good that you set the context :)

    2. It is clear that you know the need to convert the units from km/min to km/h. On the other hand, you could make it clearer by telling us why "times it by 60" in order to convert it to "h".

    3. Your explanation for part (b) on how to onvert the time in h & min to min is very clear. Good.

    4. It was good that you pointed out that since both speeds are of the same unit, there is no need for conversion :)

    5. You are also very clear on how to reduce the ratio to the simplest form :)

    6. Visual: Could zoom in so that we can see what's written clearly.

    7. It's a good attempt to guide the viewer to go follow the working.