Q&A - PSLE Math

[atutor2001]

raghupavithra:

Terry bought a vase which he decides to sell. If he sells the vase at a discount of 20%, he makes a gain of $150. If he sells it at a 45%, he loses $325. How much did Terry pay for his vase?

Must know :
Cost Price = Selling Price - Profit
Cost Price = Selling Price + Loss

At 20% discount - let the selling price be 80U
At 45% discount - let the selling price be 55U

Cost Price = 80U - 150
Cost Price = 55U + 325

80U-55U = 25U
325 + 150 = 475

25U = 475
1U = 19

Cost Price = 80U - 150 = 80x19 - 150 = 1370

[raghupavithra]

ID 26587

DifficultyDifficulty
If 2/7​ of a number equals to 4/5​ of another number, what is the smallest difference between the two numbers?

5
9
14
18
how to do this sum pls help?

[corneyAmber]

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

No. of orange flavoured jelly beans = 0.52*350 = 182

Let u be the # of orange flavoured jelly beans ate.

(182-u)/(350-u) x 100 = 44
100(182-u) = 44(350-u)
18200 - 100u = 15400 - 44u
56u = 2800
u = 50

Hence number of orange flavoured jelly beans ate is 50.

[MathIzzzFun]

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

Hi

another approach.. Number of other flavoured jelly beans remained unchanged.

Initially, other flavoured jelly beans = 48% = 168
In the end, other flavoured jelly beans = 100% - 44% = 56% = 168
Total number of jelly beans, in the end = 168 / 0.56 = 300

Number of orange flavoured jelly beans Jia Hui ate = 350 - 300 = 50

cheers.

[pecalis]

ksi:

raghupavithra:

Jia Hui had 350 jelly beans. 52% of them were orange flavoured. She ate some of the orange flavoured jelly beans and the percentage of orange flavoured jelly beans decreased to 44%. How many orange flavoured jelly beans did Jia Hui eat?

No. of orange flavoured jelly beans = 0.52*350 = 182

Let u be the # of orange flavoured jelly beans ate.

(182-u)/(350-u) x 100 = 44
100(182-u) = 44(350-u)
18200 - 100u = 15400 - 44u
56u = 2800
u = 50

Hence number of orange flavoured jelly beans ate is 50.

Alternate Solution using %:
No. of non-orange flavoured remains the same i.e. 350-182=168
This no. is changed to 100-44=56%
56%--->168
44%--->168*44/56 = 132
No. of orange flavoured eaten = 182-132 = 50

[atutor2001]

raghupavithra:

ID 26587

DifficultyDifficulty
If 2/7​ of a number equals to 4/5​ of another number, what is the smallest difference between the two numbers?

5
9
14
18
how to do this sum pls help?

Must know :

If 2/7 of a number A is equal to 4/5 of another number B,
then 4/14 of number A is equal to 4/5 of number B,
then ratio of A : B = 14 : 5

The ratio in its simplest form represents the smallest possible numbers.

So the smallest possible difference is 14 -5 = 9

[P.047330KH]

Hi, can anyone please help me solve the following questions. These are from Methodists girls school maths prelims 2010 paper. I know the answers but don’t understand how to derive at that.


1. On the reverse side of a card is a number. The decimal point of this number is shifted to the right twice. The difference between the new number and the initial number is 544.5. What is the number written on the card?

2. John and Sarah collected some cans for their project. John collected 25% more cans than Sarah. Then he gave 20 of his cans to Sarah and she had 20% more cans than him.
a) how many cans did they have in all?
b) how many more cans must John give to Sarah in order for Sarah to have 25% more than him?

[tianzhu]

P.KH:

Methodists girls school maths prelims 2010 paper.

1. On the reverse side of a card is a number. The decimal point of this number is shifted to the right twice. The difference between the new number and the initial number is 544.5. What is the number written on the card?

2. John and Sarah collected some cans for their project. John collected 25% more cans than Sarah. Then he gave 20 of his cans to Sarah and she had 20% more cans than him.
a) how many cans did they have in all?
b) how many more cans must John give to Sarah in order for Sarah to have 25% more than him?

Hi

Good Morning.

When the decimal point of a number is shifted to the right twice, it means that the original number is multiply by 100.

For example , 5.8 becomes 580.

You may use MD or UM.

Hence, initial number ------1 unit
New number ------ 100 units

Difference ------99 units ---------544.5

1 unit --------5.5


For Q2.the number of cans remains the same before and after.

(a)

At first.
John: Sarah
5:4
55:44

In the end.
John: Sarah
5:6
45:54

10 units ------ 20
1 unit -----2

99 units -----198.

(b)

20% ------- 10 cans
5% --------2 cans

John must give to Sarah 2 more cans

Best wishes

[tianzhu]

pensiveowl:

Ok thanks very much again..

Hi

Good Morning.

You're welcome.

Best wishes

[tianzhu]

mumwgals:

Thank you so much, tainzhu! Your explaination is brilliant!! :thankyou:

Hi

Good Morning.

You're welcome.

Best wishes