Q&A - PSLE Math

[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

[tianzhu]

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.

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

For Q2, note that students are asked to provide the best estimate(closest).

Best wishes

[imacsg]

Hi tianzhu,


Thanks alot.

[shurley197323]

Hi.Tianzhu. Thanks for you detail solutions. :salute:

[YumYum]

Hi, can someone pls help with the foll Qns:


1. There are 3 containers A, B and C containing alcohol solution (alcohol and water). The pure alcohol in container A is 48%. The total volume of the alcohol solution in the 3 containers is 100 litres. The volume of the alcohol solution in container A is equal to the total volume of the alcohol solution in container B and C. If we mixed the 3 containers then the alcohol in the mixture is 56%. Find the volume of alcohol in container B and C together.


2. When 2 is subtracted from the denominator of a fraction, the fraction becomes 3/4. If 9 is added to the denominator, the fraction becomes 5/7. Find the original fraction.


thanks!

[Jasmy]

Hi,need help on this qn


The ratio of boys to girls who got distinctions in a test is 4:1. This group is 1/4 of the total nos.of pupils. Half as many boys as girls got less than 60%. This is 1/5 of all the pupils. The ratio of boys to girls who scored betw 60% and distinction is 3:2. There are 22 girls in the group. How many boys achieved distinctions?

TIA