### Viva Question 4

(a) no. of parts -> 1 + 4
= 5
Volume of alcohol (1 part) -> 600 ÷ 5
= 120
Volume of alcohol is 120cm3

(b) Volume of water (4 parts) -> 600 ÷ 5 x 4
= 480
Volume of water is 480cm3

(c) 3 parts -> 480
1 part (new volume of alcohol) -> 480  ÷ 3
= 160
Difference -> 160 - 120
= 40
The amount needed is 40cm3

1. Voice is clear enough,steps are shown clearly.
Presentation:2/2
Mathematical Terms 1/1
Explanation 2/3
Understanding of concepts 2/2

2. Presentation: 2/2
Mathematical Terms: 1/1
Explanation: 2/3
Concepts: 2/2

9/10! Nice

3. 1. It's a good idea to inform the viewer with the question :)

2. In the explanation for (a), it would be good to tell right from the start how you obtain the number "5" (although you explain after telling us how you find the volume). You also mentioned how to obtain "5"; nevertheless, have not explicitly point out that 5 parts represent the volume of the solution.

3. When explaining (b), you have also mentioned to find the volume of water, it's "600 divide by 5 times 4". Since the intermediate working is already shown in the visual, it would not be necessary to read out the line "120 times 4".

4. Since you are presenting the working, it would not be appropriate to use "->". Check out how to present it to avoid ambiguity from the solution presented.

5. For part (c), you have clearly reminded us that the 3 parts in the ratio represents water and that the volume has not changed. Good :)

6. You have used the term "difference" bring out the fact there's a change of volume, that's why the need to substract the numbers. Good :)

7. The volume should be read as "cubic centimetres" instead of "c""m" "cube".

8. Note that you may want to check it out how best "cubic" can be represented when keyed into the slides.