Q&A - PSLE Math

[tianzhu]

elishatan:

Need help for 5 questions!

#3
http://elishatan.com/wp-content/uploads/2013/05/Evernote-Camera-Roll-20130506-142852-e1367824206891.jpg\">

Hi

a) n*(n+1)/2 ----- number of unshaded triangles where n is the figure number

4*(4+1)/2 ---- 4*5/2 ------ 10

b )Number of unshaded triangles in figure 50 ------ 50*51/2 ------- 1275

c)number of shaded triangles ------ (n+1)*(n+2)/2

(n+1)*(n+2) ------ 4095*2 ------ 8190

With calculator, it's not too difficult to get 89 as the answer,

n ------ 89

Best wishes

[Oldschool]

elishatan:

Need help for 5 questions!


#2
http://elishatan.com/wp-content/uploads/2013/05/Evernote-Camera-Roll-20130506-142928-e1367824147306.jpg\">

Hi

Distance Ratio,
J : D
1/3 : 1/3 + 4.5
3/3 : 3/3 + 13.5

Time taken for John to reach the library is the same as time taken by David to reach the library plus time needed to travel another 13.5km.

Time taken by David to travel 13.5 km is
= 13.5 / 15 = 0.9 hrs = 54 mins

Since David reached library at 4.45pm, then

The time when John reach the library is 5.39pm

Regards

[Oldschool]

elishatan:

Hi

http://i40.tinypic.com/315e4j5.jpg\">

Regards

[Mary Joy]

hi everyone,


I have a speed problem sum to solve.Please help me.

1.Henry took 4h to travel from A to B.Daniel took 6h to travel from B to A.When they meet,they were 1.2 km away from the midpoint.How far is the distance between A to B?

:thankyou: :lovesite:

[NYPSkiasuparent]

There are some boys and girls in the indoor sports hall. 1/2 of the number of boys in the indoor sports hall is the same as 60% of the number of girls. If there are 25 more boys than girls in the indoor sports hall, how many children are there altogether?

[PapayaDad]

There are some boys and girls in the indoor sports hall. 1/2 of the number of boys in the indoor sports hall is the same as 60% of the number of girls. If there are 25 more boys than girls in the indoor sports hall, how many children are there altogether?


B=2u
G=10p

1/2 of the number of boys in the indoor sports hall is the same as 60% of the number of girls:

u=6p

there are 25 more boys than girls:

[–u—] ; [—u—] : Boys
[pppppp] ; [pppp][25] : Girls

2p=25
10p=125 (girls)
boys = 125 +25 = 150

[Oldschool]

Mary Joy:

hi everyone,


I have a speed problem sum to solve.Please help me.

1.Henry took 4h to travel from A to B.Daniel took 6h to travel from B to A.When they meet,they were 1.2 km away from the midpoint.How far is the distance between A to B?

:thankyou: :lovesite:

Hi,

Speed Ratio,
H : D
6U : 4U

At time t, they met so

6Ut + 4Ut = AB
10Ut = AB, and

6Ut - 4Ut = 2.4
2Ut = 2.4
10Ut = 12km = AB

Regards

[NYPSkiasuparent]

Joey has some red and blue beads.

If she buys another 15 red beads, the percentage of the red beads she has become 30%.
If she gives away 20 blue beads, the percentage of the blue beads she has becomes 76%.
However many red beads and blue beads do Joey have?

[Mary Joy]

Oldschool:

Mary Joy:

hi everyone,


I have a speed problem sum to solve.Please help me.

1.Henry took 4h to travel from A to B.Daniel took 6h to travel from B to A.When they meet,they were 1.2 km away from the midpoint.How far is the distance between A to B?

:thankyou: :lovesite:

Hi,

Speed Ratio,
H : D
6U : 4U

At time t, they met so

6Ut + 4Ut = AB
10Ut = AB, and

6Ut - 4Ut = 2.4
2Ut = 2.4
10Ut = 12km = AB

Regards

thank you for your detailed explanation
:thankyou:

[Oldschool]

NYPSkiasuparent:

Joey has some red and blue beads.

If she buys another 15 red beads, the percentage of the red beads she has become 30%.
If she gives away 20 blue beads, the percentage of the blue beads she has becomes 76%.
However many red beads and blue beads do Joey have?

Hi

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?p=997662#p997662

Regards