Q&A - PSLE Math

[Tiramisu Coco]

Hi, need help for this qtn.

Thank u.

http://www.flickr.com/photos/82618212@N07/7568230484

[Tiramisu Coco]

Hi, pls help with this qtn. Thks!

http://www.flickr.com/photos/82618212@N07/7568316568

[tianzhu]

Tiramisu Coco:

Hi, need help for this qtn.

Thank u.

http://www.flickr.com/photos/82618212@N07/7568230484

Hi

Good Morning.

Where is this question from?

It should be a breeze for secondary school students who have knowledge about tangential properties.

For primary schools, it might pose some challenges.

I think one way is show is to use a pair of compasses, draw two arcs from the centre of the circle to touch the longest side of the triangle (30 cm), say at a point X.

(24 – r ) + (18 – r) ------- 30

r + r ------- 42 – 30

r ------- 12/2 ------- 6

Try it out.

Hope this helps.

Best wishes

[Tiramisu Coco]

tianzhu:

Tiramisu Coco:

Hi, need help for this qtn.

Thank u.

http://www.flickr.com/photos/82618212@N07/7568230484

Hi

Good Morning.

Where is this question from?

It should be a breeze for secondary school students who have knowledge about tangential properties.

For primary schools, it might pose some challenges.

I think one way is show is to use a pair of compasses, draw two arcs from the centre of the circle to touch the longest side of the triangle (30 cm), say at a point X.

(24 – r ) + (18 – r) ------- 30

r + r ------- 42 – 30

r ------- 12/2 ------- 6

Try it out.

Hope this helps.

Best wishes

Hi Tianzhu,
Thks for your solution.
Pls enlighten why is
(24-r)+(18-r) --- 30?

Thks!

[tianzhu]

Tiramisu Coco:

Hi, pls help with this qtn. Thks!

http://www.flickr.com/photos/82618212@N07/7568316568

Hi

This is an interesting question.

It appears wordy and lengthy, so students have to read with care. Apply your knowledge of Distance ------ Speed* Time with a bit of reasoning and you should be on the way to the solution.

The 15 minutes was saved because John’s mum did not need to travel the distance equal to the circumference of the circle.

Divide the circle into 3 parts (120 degrees).

15/3 ------ 5

John’s mum saved 5 minutes (X to school)

Hence , John’s mum travelled for 20 minutes when she met John at X.

12.35pm -------- 12.55pm

John travelled for 25 minutes (1230 ----- 1255)

25/60*6 ------ 2.5 km

John travelled for 2.5 km.

For part b, draw a timeline

From 12.35pm. add 40 minutes

12.35 ------ 12.55 -------- 1.15

5 minutes ------- 5/60 ------ 1/12h

John’mum’s speed ------- 2.5*12 ------- 30km/h

Best wishes

[tianzhu]

Tiramisu Coco:

Hi Tianzhu,
Thks for your solution.
Pls enlighten why is
(24-r)+(18-r) --- 30?

Thks!

Hi

This question is pretty interesting.

This is a right angled triangle.

May I suggest you take out a pair of compasses and draw the arcs(points where the circle touches the triangle at right angles).

The two arcs meet the same point X on the longest side of the triangle.

After drawing, you’ll see why (24-r) + (18-r) add up to be equal to 30.

Best wishes

[MathIzzzFun]

Tiramisu Coco:

tianzhu:

Hi, need help for this qtn.

Thank u.

http://www.flickr.com/photos/82618212@N07/7568230484

Hi

Good Morning.

Where is this question from?

It should be a breeze for secondary school students who have knowledge about tangential properties.

For primary schools, it might pose some challenges.

I think one way is show is to use a pair of compasses, draw two arcs from the centre of the circle to touch the longest side of the triangle (30 cm), say at a point X.

(24 – r ) + (18 – r) ------- 30

r + r ------- 42 – 30

r ------- 12/2 ------- 6

Try it out.

Hope this helps.

Best wishes

Hi Tianzhu,
Thks for your solution.
Pls enlighten why is
(24-r)+(18-r) --- 30?

Thks!

Hi

This is not a standard P6/PSLE question - more likely a competition question, because this requires student to know properties of tangent, congruent triangles.

http://i46.tinypic.com/219bfx2.png\">

BY=BZ (by congruent triangles: OY=OZ, OB=OB, angle OZB=angle OYB=90 deg)
CX=CZ (by congruent triangles)

BY+CX = BZ + CZ
24-R + 18-R = 30, R --> radius of circle

cheers.

[underthesea]

Can someone help me to solve this question without using algebra.


Tank A and tank B contain some water.
If 46.5ml of water is drained out from tank A, the volume of the water in tank A will be 60% that of the water in tank B.
If 35.2ml of water is drained out from tank B, the volume of water in tank B will be 85% that of the water in tank A.
What is the total volume of water in tank A and tank B?

TIA.

[tianzhu]

underthesea:

Can someone help me to solve this question without using algebra.


Tank A and tank B contain some water.
If 46.5ml of water is drained out from tank A, the volume of the water in tank A will be 60% that of the water in tank B.
If 35.2ml of water is drained out from tank B, the volume of water in tank B will be 85% that of the water in tank A.
What is the total volume of water in tank A and tank B?

TIA.

Hi

Thsi question has been discussed before.

Hope this helps.

Best wishes

http://farm7.staticflickr.com/6166/6162256981_fb0d5c4e9e_z.jpg\">

[Tiramisu Coco]

MathIzzzFun:

Tiramisu Coco:

[quote=\"tianzhu\"]Hi, need help for this qtn.

Thank u.

http://www.flickr.com/photos/82618212@N07/7568230484

Hi

Good Morning.

Where is this question from?

It should be a breeze for secondary school students who have knowledge about tangential properties.

For primary schools, it might pose some challenges.

I think one way is show is to use a pair of compasses, draw two arcs from the centre of the circle to touch the longest side of the triangle (30 cm), say at a point X.

(24 – r ) + (18 – r) ------- 30

r + r ------- 42 – 30

r ------- 12/2 ------- 6

Try it out.

Hope this helps.

Best wishes

Hi Tianzhu,
Thks for your solution.
Pls enlighten why is
(24-r)+(18-r) --- 30?

Thks!

Hi

This is not a standard P6/PSLE question - more likely a competition question, because this requires student to know properties of tangent, congruent triangles.

http://i46.tinypic.com/219bfx2.png\">

BY=BZ (by congruent triangles: OY=OZ, OB=OB, angle OZB=angle OYB=90 deg)
CX=CZ (by congruent triangles)
BY+CX = BZ + CZ
24-R + 18-R = 30, R --> radius of circle

cheers.[/quote]Hi tianzhu & MathIzzzfun,
Thks for your help.
A friend shared this qtn that she got from a pri maths tuition ctr's FB pg, which stated that to solve the qtn, students need to draw lines, use ratio & unit transfer method(2 variables concepts). Wonder if it's relevant for p6 to know how to solve this type of qtns.