tianzhu:

jewelbox:

Thanks Tianzhu, you are fast. I will slowly digest your solutions. Meanwhile i have prob solving this qn. Thanks. http://i42.tinypic.com/zbp0o.jpg\">

Hi

Good Morning.

Imagine you are seeing a reflection of the picture or image. Flip the image so that you can see a square formed by the two isoceles triangles.

Find the area of (Area of quadrant – Area of isosceles triangle) and divide it by 2.

Area of quadrant ------ 38.5

Area of isosceles triangle ------ 24.5

38.5 – 24.5 ------14

Difference in shaded area ----- 14 /2 ------ 7

Best wishes

Hi Tianzhu
I'm afraid I'm a bit weak in geometry. Hard to visualize things.
I can see the area of a quadrant, which is 1/4 of area of circle, radius 7cm. I can also see the area of isosceles triangle, which is 1/2 area of square.
But I don't see how (area of quadrant - area of triangle)/2 leads to difference in the 2 shaded regions.

MathIzzzFun:

mathnoobs:

[quote=\"Zack7\"]
Ratios are about scaling. You don't have to multiply them, just that u will b working with fractions.

yes, but it is not easy to see the scaling factor, until you go through the entire question, mull through it and figure out which numbers you need to equalize. In this case, have to scale twice, so not so easy to see upfront. I think under exam conditions, very difficult to see how to scale it so that the relevant numbers are equal. Even under non exam conditions, for me, it was difficult to see which numbers can be equalized and thus scaling is applied.

Hi

students learn in lower primary how to \"scale\" using models. eg. Alice had twice as much money as Mary. If they had $30 altogether, how much did each have?

The model drawing will show 2 blocks for Alice, 1 block for Mary. Total 3 blocks representing $30

eg. The number of red marbles to the number of blue marbles in a box is in the ratio of 2 : 7. If there are 63 marbles altogether, how many red marbles are there ?
The model drawing will show 7 blocks for blue marbles, 2 blocks for red marbles, total 9 blocks representing 63.

In the question above, when we arrive at the ratio Kumar: Leon: Max-->12:8:9, we can work with these numbers directly ie 12u:8u:9u

Max has 9u. Since he had twice after receiving the bookmarks from the others, he received 9u.
So, total number contributed by both kumar and leon is 9u, in the ratio of 3:1 --> back to the examples above: Kumar 3 blocks, Leon 1 block, total 4 blocks for 9u, so 1 block --> 9u/4

Kumar gave 3 blocks --> 3x 9u/4 = 27u/4
Leon gave 1block --> 9u/4

Left, Kumar : Leon --> 12u-27u/4 : 8u-9u/4 --> 21u/4 : 23u/4 --> 21u:23u ... so we get to the same final ratio. the only difference is that when we work with the numbers directly, we will have to work with fractions - which many students dislike

good night !

cheers.[/quote]Hi MathIzzzfun
thank you for your example. It has helped me in understanding scaling. I guess I'll need more practise in this area to be really familiar with the concept. For simple one step scaling, I'm alright, but for the scaling as required by this problem sum, it is a little bit more difficult to grasp.

Zack7:

* i have to say these questions are quite tricky, harder than the questions i see at the p6 section

yes, pity our poor children.... so little time for play now....it's just mug, mug, mug...

Zack7:

Ratios are about scaling. You don't have to multiply them, just that u will b working with fractions.

yes, but it is not easy to see the scaling factor, until you go through the entire question, mull through it and figure out which numbers you need to equalize. In this case, have to scale twice, so not so easy to see upfront. I think under exam conditions, very difficult to see how to scale it so that the relevant numbers are equal. Even under non exam conditions, for me, it was difficult to see which numbers can be equalized and thus scaling is applied.

mathnoobs:

MathIzzzFun:

[quote=\"lousymum\"]pls help


kumar had 50% more bookmarks than leon.
max had 75% as many bookmarks as kumar.
kumar and leon gave max a number of bookmarks in the ratio 3:1.
as a result, max had twice as many bookmarks as before, and leon had 16 bookmarks more than kumar.
how many bookmarks did kumar give to max?

tia

Hi

Kumar:Leon --> 3:2
Kumar:Max --> 4:3
Kumar : Leon : Max --> 12 : 8 : 9 --> 48u : 32u : 36u

Max received a total of 36u of bookmarks from Kumar & Leon in ratio of 3:1,
Bookmarks given by Kumar : Leon --> 27u : 9u
Bookmarks left, Kumar : Leon --> 21u : 23u
2u --> 16, 1u --> 8

Bookmarks given by Kumar to Max --> 8 x 27 = 216

cheers.

I'm afraid this is very deep for me. How do I know that I have to multiply 12:8:9 by 4 ? also how do I know that I have to multiply 3:1 by 9 ?[/quote]never mind. I finally figured it out. Still very deep though.

MathIzzzFun:

lousymum:

pls help


kumar had 50% more bookmarks than leon.
max had 75% as many bookmarks as kumar.
kumar and leon gave max a number of bookmarks in the ratio 3:1.
as a result, max had twice as many bookmarks as before, and leon had 16 bookmarks more than kumar.
how many bookmarks did kumar give to max?

tia

Hi

Kumar:Leon --> 3:2
Kumar:Max --> 4:3
Kumar : Leon : Max --> 12 : 8 : 9 --> 48u : 32u : 36u

Max received a total of 36u of bookmarks from Kumar & Leon in ratio of 3:1,
Bookmarks given by Kumar : Leon --> 27u : 9u
Bookmarks left, Kumar : Leon --> 21u : 23u
2u --> 16, 1u --> 8

Bookmarks given by Kumar to Max --> 8 x 27 = 216

cheers.

I'm afraid this is very deep for me. How do I know that I have to multiply 12:8:9 by 4 ? also how do I know that I have to multiply 3:1 by 9 ?

KSgal:

chokos:

Hi all,

Thanks for helping.
I need help to solve the following questions:

Q 1) Some pupils from 5K, 5L and 5M took part in a Social Studies quiz. 34 participants were from 5L and 5M. 21 participants were not from 5L and 19 participants were not from 5M. How many pupils from these 3 classes took part in the quiz? Model Answer: 37pupils

5L + 5M: 34

21 not from 5L means that the 21 are from 5K + 5M

19 not from 5M means that the 19 are from 5K + 5L

Notice that if you add all the numbers up, you will get 2 5K, 2 5L and 2 5M.

So:

2 5K, 2 5L, 2 5M--34+21+19=74
No. of pupils from all 3 classes (1 5K, 1 5L, 1 5M)--74/2=37

Ans: 37 pupils

Hope this helps ^_^

I'm afraid I'm totally lost here. I only got up to this stage:
http://i41.tinypic.com/2v1upf4.png\">

maybe you can help to fill up the diagram. I don't understand where the 2 5K comes from, or the 2 5L...

tianzhu:

You’re welcome.

You’re definitely not a “blur” mummy like you mentioned. On the contrary, the way you dissected the points in the questions and your ability to ask penetrating questions shows an enthusiastic and dynamic mummy.

thank you for the kind words, Tianzhu.
It made my day. :rahrah:
have a great week.

tianzhu:

mathnoobs:

Hi Tianzhu
my child is in P5. The questions are mine. I have to be clear before I can teach my child or else it's the blur teaching the blur.
I do have a copy of the Challenging Maths. However, they don't really talk about question interpretation. The questions there are more straight forward in terms of interpretation.

I did work out the Don problem sum with the 1/4 based on the remainder savings and it came out as a decimal number, so that can't be right.

Hi

It’s good to know you found the questions in Challenging Maths more straight forward in terms of interpretation. It shows you have grasped the concepts well.

Your child is in P5, those two questions are for P6, so he doesn’t know them now because he hasn’t been taught yet. Once he learns from his teacher, he’ll know how to do them. So don’t worry too much now.

I am sure you are familiar with this question.

Mrs Jaya spent $162 on a present for her husband. She spent 5/11 of the remaining money on a purse for herself. If she had 3/7 of her money left, how much money did Mrs Jaya have a first?

Please refer to an example of a similar question under 1.2, page 3 of CM.

Now let us look at Don’s question.

Don spent $268 of his savings on a camera and 3/8 of the remainder on a pair of shoes. Then, he bought a bag for $62 and had 1/4 of his savings left. How much savings did Don have at first?

Please refer to my solution to Rice last night.

Don had $612 at first. He went on to spend $268 on a camera, leaving a remaining amount of $129 (3/8 of $344).Then he bought a bag for $62, leaving a remaining amount of $153 (1/4 of savings left).

For the Nicole question,please read sentence by sentence and understand the context.

I think you'll find it clear enough to know that the 40% of the savings is based on the remaining amount of her money in March and not on her original savings in Jan.

Best wishes

Hi Tianzhu
thank you very much for spending so much time to explain the concepts to me. I really do appreciate it.
I guess the only way reinforce the concept will be to do more such similar questions. The Mrs Jaya question helped. I wonder if there's more of the Nicole type of questions.
Anyway, I have to move on to other question types. There's just so much to cover.
thanks again and have a great evening.

tianzhu:

Hi

I am sorry; I can’t answer your question in detail now.

Just curious, are these questions from the mummy or from your child?

Is your child in P5 or P6?

If your child is in P5, higher order questions on remainder concept may not be covered by his/her teacher yet as the year is still quite young.

If you have a copy of Challenging Maths Made Easy, I suggest you look at the chapter on Remainder Concept.

Perhaps you may want to work out the answer based on the way you described. You may appreciate the situation better.

Best wishes

Hi Tianzhu
my child is in P5. The questions are mine. I have to be clear before I can teach my child or else it's the blur teaching the blur.
I do have a copy of the Challenging Maths. However, they don't really talk about question interpretation. The questions there are more straight forward in terms of interpretation.

I did work out the Don problem sum with the 1/4 based on the remainder savings and it came out as a decimal number, so that can't be right.