Q&A - PSLE Math

[BigDevil]

@ozora

I have 288 also.
Care to show your working?

[ozora]

Hi,
the following question is from CHIJ Prelim maths 2015.

Q16. A fruit stall owner had some pears, apples and oranges.
For every 2 pears, there were 3 apples.
For every 9 apples, there were 5 oranges.
36 pears were rotten and thrown away.
Then 1/5 of the remaining fruits were pears.
How many fruits did the fruit owner have at first?
Is the answer 240 or 288?
I used one quantity unchanged method which is the apples and oranges unchanged , the result is 240.
If I used all quantities changed method, the result is 280 which is same as the given answer.
Could anyone point out the error?

I've got 288...not 280

Saw my mistake.
Why is it we have to use all changes ? Can't we assume that oranges and apples are constant as they have no changes?

[ozora]

Need assistance in the following question
Q1. CHIJ Prelim Maths 2015
Q11. A pen cost $0.95 more than a pencil.
Cat bought twice as many pencils as pens.
she spent a total of $53.60.
She spent a total of $2.40 more on the pens than the pencils.
HOw many pens did Cat buy?

I used Units X Value method but couldn't solve it.
Hopefully, someone could guide me through it
Thanks
@John thanks for pointing the error.

Anyone knows how to solve this .
Thanks

[Ender]

Need assistance in the following question
Q1. CHIJ Prelim Maths 2015
Q11. A pen cost $0.95 more than a pencil.
Cat bought twice as many pencils as pens.
she spent a total of $53.60.
She spent a total of $2.40 more on the pens than the pencils.
HOw many pens did Cat buy?

I used Units X Value method but couldn't solve it.
Hopefully, someone could guide me through it
Thanks
@John thanks for pointing the error.

Anyone knows how to solve this .
Thanks

Straight away find how much she spent for pens in total, likewise for pencil.
Total spending for pencil =( 53.60 - 2.40) /2 =$ 25.60
Total spending for pens = 25.6 +2.4= $28

She bought twice as many pencils as pen. So let qty of pencils be 2u and pens be 1u.

2u of pencils cost $25.60
1u of pencils cost $12.80

1u of pens cost $28

Difference in cost of 1u of pens and 1u pencils=28-12.8= $15.20

So 1u = 15.2/0.95= 16.

And number of pen she bought is 1u, also 16###

[Ender]

Hi,
the following question is from CHIJ Prelim maths 2015.

Q16. A fruit stall owner had some pears, apples and oranges.
For every 2 pears, there were 3 apples.
For every 9 apples, there were 5 oranges.
36 pears were rotten and thrown away.
Then 1/5 of the remaining fruits were pears.
How many fruits did the fruit owner have at first?
Is the answer 240 or 288?
I used one quantity unchanged method which is the apples and oranges unchanged , the result is 240.
If I used all quantities changed method, the result is 280 which is same as the given answer.
Could anyone point out the error?

I've got 288...not 280

Saw my mistake.
Why is it we have to use all changes ? Can't we assume that oranges and apples are constant as they have no changes?

Your working is right. And Apples and Oranges remains the same. Only the number of Pears is reduced. I don't see any indication in your working to indicate otherwise.

[BigDevil]

Hi,
the following question is from CHIJ Prelim maths 2015.

Q16. A fruit stall owner had some pears, apples and oranges.
For every 2 pears, there were 3 apples.
For every 9 apples, there were 5 oranges.
36 pears were rotten and thrown away.
Then 1/5 of the remaining fruits were pears.
How many fruits did the fruit owner have at first?
Is the answer 240 or 288?
I used one quantity unchanged method which is the apples and oranges unchanged , the result is 240.
If I used all quantities changed method, the result is 280 which is same as the given answer.
Could anyone point out the error?

I've got 288...not 280

Saw my mistake.
Why is it we have to use all changes ? Can't we assume that oranges and apples are constant as they have no changes?

Of course you can keep O and A constant.
The trick is to use the correct number of u's.

So, instead of having P as 6u and O+A as 14u, we have
P -> 12u
O+A -> 28u

After throwing away 36 pears, we have
P -> 7u
O+A -> 28u

Change in pear -> 5u = 36
Total at first -> 40u = 36 x 8 = 288

As you can see, 28u was chosen to represent O+A because it was
the LCM of 14 and 4, making it divisible by 4 to give us 7u to
represent the number of pears after the change. By doing so,
you can eliminate the need to introduce 1p and 4p into the solution.

Hope this helps.

[Nebbermind]

I didn't use U and P.

Apple is common in the two ratio. I combined them to give

po => 6u : 9u : 5u

5*(6u-36) = 20u-36
=> 30u - 180 = 20u - 36
=> 10u =144
Therefore 20u = 288

[ozora]

@Ender
@BigDevil
@Nebbermind
Thanks for the guidance and tips.

[Steadyberry]

Hi pls help. This question is from eph preparing for psle maths.

A pie chart shows how a sum of money was shared among four men. (Sorry have problem posting the pie chart).
Max 25% of pie chart
John 30% of pie chart
Bobby unknown %
Ivan unknown %

Ivan's share was 70% more than Bobby's share. If the sum of money was $21600, how much money did Ivan get?

Thanks

[alfretztay]

Hi pls help. This question is from eph preparing for psle maths.

A pie chart shows how a sum of money was shared among four men. (Sorry have problem posting the pie chart).
Max 25% of pie chart
John 30% of pie chart
Bobby unknown %
Ivan unknown %

Ivan's share was 70% more than Bobby's share. If the sum of money was $21600, how much money did Ivan get?

Thanks

100 - 25 - 30 = 45

45% x 21600 = 9720

270% ------- 9720

1% ------- 9720/270 = 36

170%------- 170 x 36 = 6120

For easier understanding :

Max ------- 25% x 21600 = 5400

John ------- 30% x 21600 = 6480

21600 - 6480 - 5400 = 9720

Bobby ------- 100%

Ivan ------- 170%

270% ------- 9720

1% ------- 9720/270 = 36

170%------- 170 x 36 = 6120



Ans : $6120.