Question 6 :

a) i) a:b = 1 1/2 : 2 2/5

= 1.5 : 2.4

-changed to nearest whole number-

= 30 : 48

-simplified-

= 15 : 24

= 5 : 8

ii) b:c = 0.105 : 0.350

-changed to whole number-

= 105 : 350

-simplified-

= 21 : 70

= 3 : 10

b) a:b = 5:8

b:c = 3:10

Since 'b' is the repeated value in both ratios , the ratios have to be multiplied so that the value of 'b' will be the same in both ratios .

a:b = 15:24

b:c = 24:80

a:b:c = 15:24:80

c) a+b+c = 119 units

$500 ÷ 119 * 15 ( Alan's share in units )

≈ $63.03 (2 d.p)

mathematical terms [1]

ReplyDeleteexplanation of working/solution must be clear [3]

understanding of concept [2]

accuracy of answers [2]

presentation [1]

- you are pointing to the different mathematical statement that you are explaining.

- there is some background noise and the video is a little jerky

Presentation [1/2]

ReplyDelete-She was pointing at the wrong part of the solution while she was explaining another part.

Mathematical terms [1/1]

Explanation of working/solution must be clear [2/3]

-She said '8/10' for part (b), when it was supposed to be '3/10'

Understanding of concepts [2/2]

Accuracy of answer [2/2]

Total: 8/10

Note: Comments are made reference to the clip copied submitted separately (offline).

ReplyDeletePS: @DYS (Gladys?) @Jonathan - the misalignment was due to errors when clip uploaded online.

1. For (a),

in (i) you mentioned the the ratio "is also equal to 1.5 is to 2.4". Why? Will need to elaborate why changing them to decimals first. Why convert to the nearest who number? How to get "30 is to 48"? Also, good to explain how to go about simplifying? Say, we find the highest common factor of the 2 numbers and divide both numbers by HCF so as to express ratio in its simpest form.

The above comments also apply to your explanation to (ii)

2. For (b), you have correctly pointed out that "b" is common between the 2 ratios. Use the word "common" instead of saying "b is a repeated value in the ratio".

3. You have also articulated the reason why we need to multiple the value to the 2 ratios (i.e. so that they are the "same"). Good. Also, do add on that only when "b" has the same number of parts in both ratios, then we could merge the ratios.

4. Why multiple the first ratio by "3" and the second one by "8"? Elaborate how you arrive at these magic numbers (something like, to find the lowest common multiple between the 2 values)?

5. Explanation for (c), in general, is clear :)

However, what's the answer to (c)? You concluded the presentation by saying "round off the answer to 2 decimal place". So, what's the answer?