Q&A - PSLE Math

[N3SKiasu]

Hi, kindly help with this question:


In a classroom, when a boy stands up, the number of boys sitting becomes 4/5 of the number of girls sitting. On the other hand, when a girl stands up, the number of girls sitting becomes 8/7 of the number of boys sitting. How many boys and girls are there in the class altogether?

Question looks similar to the Mary & Peter question but still can't figure out. :oops: pls help.

[Dharma]

N3SKiasu:

Hi, kindly help with this question:


In a classroom, when a boy stands up, the number of boys sitting becomes 4/5 of the number of girls sitting. On the other hand, when a girl stands up, the number of girls sitting becomes 8/7 of the number of boys sitting. How many boys and girls are there in the class altogether?

Question looks similar to the Mary & Peter question but still can't figure out. :oops: pls help.

http://www.postimage.org/

[Drdj]

Dear all,


Could you explain the solution of this sum from Ai Tong 2008?
The triangles are both isoceles (45, 45, 90), but I just can't seem to get it
Thanks in advance

http://www.postimage.org/image.php?v=Pq9MGnr

[JustKP]

Drdj:

Dear all,


Could you explain the solution of this sum from Ai Tong 2008?
The triangles are both isoceles (45, 45, 90), but I just can't seem to get it
Thanks in advance

http://www.postimage.org/image.php?v=Pq9MGnr

Hi, just joined the 2 triangles together to get an isoseles triangle of both sides 10cm (radius of the circle).

[kiasiparent]

Drdj:

Dear all,


Could you explain the solution of this sum from Ai Tong 2008?
The triangles are both isoceles (45, 45, 90), but I just can't seem to get it
Thanks in advance

http://www.postimage.org/image.php?v=Pq9MGnr

There are two smaller and unshaded triangles inside the semi circle. These two triangles can be rearranged to form a square of diagonal 10 cm.
Area of square = diagonal x diagonal / 2 = 10 x 10 / 2 = 50

Then take area of semi circle - 50

[Drdj]

Dear JustKP,


Thanks so much !!

JustKP:

Drdj:

Dear all,

Could you explain the solution of this sum from Ai Tong 2008?
The triangles are both isoceles (45, 45, 90), but I just can't seem to get it
Thanks in advance

http://www.postimage.org/image.php?v=Pq9MGnr

Hi, just joined the 2 triangles together to get an isoseles triangle of both sides 10cm (radius of the circle).

[Drdj]

Dear all,


Could you help me to solve this?
Thanks a lot
http://www.postimage.org/image.php?v=aV15TSLS

[JustKP]

Drdj:

Dear all,


Could you help me to solve this?
Thanks a lot
http://www.postimage.org/image.php?v=aV15TSLS

Angle AED is 90, so angle DAE is 27. Thus angle x is 36 (90-27-27).

[Drdj]

Thanks again

JustKP:

Drdj:

Dear all,

Could you help me to solve this?
Thanks a lot
http://www.postimage.org/image.php?v=aV15TSLS

Angle AED is 90, so angle DAE is 27. Thus angle x is 36 (90-27-27).

[suiyuan]

Thank You for your help.

Please help me solve these questions in a non-algebraic manner.

Q1) A motorist takes 1/2 h less than the usual time to travel from KTown to JTown when he increases his average speed by 10%. For a distance of 100km, he will take 1/3 h less than the usual time if his speed is 20% more than the average speed from KTown to JTown. Find the distance between KTown and JTown.

Q2) A car travels from town P to town Q at a constant speed. When it increases its speed by 20%, the journey from P to Q takes 1 hour less than its usual time. When it travels at its usual speed for 100 km before increasing its speed by 30%, the journey also takes 1 hour less than usual. Find the distance between the two towns.