Q&A - P5 Math

[carol73]

pls help to provide ans to the below, I want to confirm if my solution is correct


There were 147 glasses for sale. 10/21 of them were blue and the rest were yellow. When some blue glasses were sold, the number of blue glassess left was 4/15 of the total number of glasses left, how many blue glasses were sold.


there were 889 pupils in a school. 1/3 o fthe girls and 1/2 of the boys were in the upper primary classess. there were equal number of boys and girls in the lower primary classes. find the number of girls and the number of boys in the school

[ChewingPencilLine]

carol73:

pls help to provide ans to the below, I want to confirm if my solution is correct


There were 147 glasses for sale. 10/21 of them were blue and the rest were yellow. When some blue glasses were sold, the number of blue glassess left was 4/15 of the total number of glasses left, how many blue glasses were sold.


there were 889 pupils in a school. 1/3 of the girls and 1/2 of the boys were in the upper primary classes. there were equal number of boys and girls in the lower primary classes. find the number of girls and the number of boys in the school

Q1: 42
Q2: 381 girls, 508 boys

[tianzhu]

Jamesbond:

http://i46.tinypic.com/161ant.jpg\">

Pl help....

Hi

Good Morning.

Area of triangle ABC ------ 315*2 -------630

Divide the square in triangle XYZ into 4 smaller triangles; you will see that triangle XYZ has 9 such small triangles altogether.

Hence the area of square in triangle XYZ ------4/9*630 ------ 280

Best wishes

[Jamesbond]

tianzhu:

Jamesbond:

http://i46.tinypic.com/161ant.jpg\">

Pl help....

Hi

Good Morning.

Area of triangle ABC ------ 315*2 -------630

Divide the square in triangle XYZ into 4 smaller triangles; you will see that triangle XYZ has 9 such small triangles altogether.

Hence the area of square in triangle XYZ ------4/9*630 ------ 280

Best wishes

Good morning Tianzhu....I got it. Thanks for ur help.

[Jamesbond]

http://i50.tinypic.com/35kivcm.jpg\">

Help needed.

[tianzhu]

Jamesbond:

http://i50.tinypic.com/35kivcm.jpg\">

Help needed.

Hi

The logic behind this question is similar to your earlier one.

Best wishes

[Jamesbond]

tianzhu:

Jamesbond:

http://i50.tinypic.com/35kivcm.jpg\">

Help needed.

Hi

The logic behind this question is similar to your earlier one.

Best wishes

Actually I worked out this sum. For (a) I had a doubt of including the smaller sq W in calculating the area of sq MQPN. For (b) my ans is 200. Ans in ans sheet is 225. Can u let me know the correct ans.

[Jamesbond]

http://i50.tinypic.com/zv5r3l.jpg\">

Find the angle EDF.....pl help.

[redruby]

At a concert, the ratio of the number of women to the number of men is 3:1. The ratio of the number of women to the number of children is 1:4. What is the ratio of the adults to the number of children at the concert?

[cimman]

Jamesbond:

http://i46.tinypic.com/161ant.jpg\">

Pl help....

the key thing to note in such problems is to figure out how to fit one shape onto another shape. That's easier said than done for some children who don't have the gift of spatial visualization. However, there are some general rules one can follow in the case of isosceles triangles and square.
http://i48.tinypic.com/1z4fnvb.png\">
Step 1: convert the triangles to a square. ie. a square is made up of 2 isosceles
triangles. The concept of tessellation is important here. Tessellate the triangle till you get a square.
http://i49.tinypic.com/dnha40.png\">

Step 2: draw lines to connect the vertices of the square together.
http://i46.tinypic.com/iqkgie.png\">

Step 3: from here, you should be able to pick out a unit shape (typically the smallest shape) that can be tessellated to fill the larger shape.
http://i47.tinypic.com/mvn347.jpg\">

The key point here is to tessellate the smaller regular shape to get the larger regular shape. You can view tessellation as a mirror reflection. Reflect the isosceles triangle till you get a square.
http://i47.tinypic.com/witu94.png\">

if you're ever stuck, start drawing lines to connect vertices of the regular shape, and then see if the smaller shapes that came out of that drawing can be tessellated to fill the larger shape.
I call this heuristic: Vertex Connection.