Q&A - PSLE Math

[Nebbermind]

mumworks:

Hi,


How to explain to the kid this type of qs ?

In a group of 9 pupils, there are 4 boys.
Mr Tan wants to pair off each girl with a boy for a project.
How many different ways can he pair off a boy with a girl ?

Thank you very much.

it looks somewhat like GEP or MO qn!!

I 'revised' for psle some yrs ago...never came across this type of qn.

[imacsg]

Ai Tong CA1 Q14


Can someone help me?
Amy savings was 40% less than Baoyu’s saving at first. After Amy donated $52 and Baoyu donated $60, Baoyu’s savings became 5 times as much as Amy. What was their total savings at first?

Which of the following is the best estimate of 55 x 249?
Ans is 50 x 250. But why not 60 x 200?
1. 50 x 200
2. 50 x 250
3. 60 x 200
4. 60 x 250

Thanks.

[2DMommy]

My boy’s homework, appreciate your help.


1) Andrew had some red apples and green apples to sell 3/5 of them were red apples and the rest were green apples. After he sold of 5/6 the red apples and 100 green apples, he had 1/4 of the apples left. How many apples did he have altogether at first ?

2) Harry shared his money with Rosa in the ratio 9:7. When Harry spent $67.50 and Rosa spent $90, the new ratio of his money to Rosa’s money became 9:4.
a) How much did Rosa have left ?
b) How much did Harry Have at first ?

Thank you !

[tianzhu]

2DMommy:

2) Harry shared his money with Rosa in the ratio 9:7. When Harry spent $67.50 and Rosa spent $90, the new ratio of his money to Rosa's money became 9:4.
a) How much did Rosa have left ?
b) How much did Harry Have at first ?

Hi

You may use \"Units and Parts\"

At first
Harry: Rosa ------- 9u:7u

Change
Harry: Rosa ------- -67.50:-90

In the end
Harry: Rosa ------- 9p:4p

Equalise the parts.

(9u – 67.5) ----- 9p
(x4)
36u - 270 ------ 36p

(7u - 90) ----- 4p
(x9)
63u - 810 ------36p

36u - 270 ----- 63u - 810
27u ------ 540
u ------ 20

Amount of money Rosa left ------ (7*20) - 90 ------ 50

Amount of money Harry had at first ------- 9*20 ------ 180

Best wishes

[shurley197323]

Hi,pls help. I got 3 qtns from Aitong CA 1paper.


1) In a boutique,the no of dresses sold was 70.This was 40% more than the no of blouses sold. How many blouses were sold
My answer is 42, Paper answer is 50

2) X,Y & Z bought a watch for their mum. X paid 1/4 of what Y & Z paid. Y paid 1/5 of what X and Z paid. If Z paid $56 more than Y, how much did the watch cost.
Answer :$120

3)Amy saving was 40% less than baoyu at first. After Amy donated $52 and baoyu donated $60. Baoyu saving becomes 5 times as much as AMy. What was their saving at first?
Answer : $160.

Thanks in advance.

[tianzhu]

shurley197323:

1) In a boutique,the no of dresses sold was 70.This was 40% more than the no of blouses sold. How many blouses were sold
My answer is 42, Paper answer is 50

2) X,Y & Z bought a watch for their mum. X paid 1/4 of what Y & Z paid. Y paid 1/5 of what X and Z paid. If Z paid $56 more than Y, how much did the watch cost.
Answer :$120

Hi

Q1)
140% ------ 70
100% -------70*100/140 -------- 50(blouse)

Q2)
A common multiple of 5 and 6 is 30

X ------ 6 units
Y ------ 5 units
Z ------- 19 units

14 units ------ 56
1 unit ------- 4

30 units ------- 120(watch cost)

Best wishes

[tianzhu]

shurley197323:

3)Amy saving was 40% less than baoyu at first. After Amy donated $52 and baoyu donated $60. Baoyu saving becomes 5 times as much as AMy. What was their saving at first?
Answer : $160.

Hi

You may use \"Units and Parts\"

Amy:Baoyu ------ 60:100----- 3:5

At first
Amy:Baoyu ------3u:5u

Change
Amy:Baoyu -------- -52:-60

In the end
Amy:Baoyu ------1p:5p

Equalise the parts.

(3u – 52) ----- 1p
(x5)
15u - 260 ------ 5p

15u - 260 ----- 5u - 60
10u ------ 200

u ------ 20

Their savings at first ------- 8*20 ------ 160

Best wishes

[tianzhu]

mumworks:

Hi,


How to explain to the kid this type of qs ?

In a group of 9 pupils, there are 4 boys.
Mr Tan wants to pair off each girl with a boy for a project.
How many different ways can he pair off a boy with a girl ?

Thank you very much.

Hi

The answer is 5*4 -----20.

You may use \"Systematic Listing\" or use a Tree Diagram.

Best wishes

[portal]

Why is maths so hard :?

[tianzhu]

2DMommy:

1) Andrew had some red apples and green apples to sell 3/5 of them were red apples and the rest were green apples. After he sold of 5/6 the red apples and 100 green apples, he had 1/4 of the apples left. How many apples did he have altogether at first ?

Hi

Draw a bar and divide into 20 equal units.

12 units ------ red apples
8 units ------ green apples

5/6 of red apples sold ---------- 10 units
Red apples left ------- 12-10 ------- 2 units

1/4 of the apples left -------- 5 units

Green apples left ------- 3 units
Green apples sold ------- 8-3 -------- 5 units

5 units ------- 100
1 unit ------ 20

20 units -------- 400 (number of apples at first)

Best wishes