Q&A - PSLE Math

[fightingmom]

MathIzzzFun:

fightingmom:

Hi,


Please help with the following question:

Miss Koh had 130 apples and oranges. After she sold 2/3 of the apples and 2/5 of the oranges, she had 36 more oranges than apples left. How many fruits had she left ?

TIA!

After sales of 2/3 of apples & 2/5 of oranges, number of apples and oranges remaining:
Apples (1/3) --> 3 units
Oranges (3/5) --> 3 units + 36 = 3 x (1 unit + 12)

At first,
Apples --> 9 units
Oranges --> 5 units + 60
Total --> 14 units + 60 = 130
1 unit --> 5

Number of fruits left:
Apple --> 15
Oranges --> 51
Total --> 66

cheers.

:thankyou: MathIzzzFun!

[fightingmom]

MathIzzzFun:

fightingmom:

Hi,


Sorry can also help with another question?

There are some chairs in a hall. 1/2 of them are put in short rows and 2/5 of them are placed in long rows. The remaining chairs are placed at the back of the hall. There are 20 short rows and 6 long rows. Each long row has 20 more chairs than each short rows. How many chairs are there in all ?

TIA!


I worked out and my answer is 208 ... Doesn't seem right though ....

Ratio of chairs in short rows : long rows : back of hall = 1/2 : 2/5 : 1-1/2-2/5 = 5 : 4 : 1--> 20u : 16u : 4u --- total 40u

For long rows,
16u = 6u + 6 x 20
1u --> 12
Total number of chairs --> 40 x 12 = 480

cheers.

:thankyou: MathIzzzFun! You have worked out such simple steps ! My initial working was complicated until I was :? too ! Thanks once again!

[fightingmom]

speedmaths.com:

fightingmom:

Hi,


Please help with the following question:

Miss Koh had 130 apples and oranges. After she sold 2/3 of the apples and 2/5 of the oranges, she had 36 more oranges than apples left. How many fruits had she left ?

TIA!

Hi,

One possible method:
Using the Advanced Model Method
(or Bags and Boxes Method)

Look at the 2 denominators; 3 and 5.

Let Miss Koh put the apples in 3 Bags.
Let Miss Koh put the oranges in 5 Boxes.

Miss Koh had 130 apples and oranges
3 Bags and 5 Boxes contain 130 fruits.
3 Bags + 5 Boxes → 130 fruits
3 Bags → 130 fruits - 5 Boxes .............. (Row 1)

She sold 2/3 of the apples and 2/5 of the oranges
She sold 2 Bags and 2 Boxes of fruits.
She had 1 Bag and 3 Boxes of fruits left.

She had 36 more oranges than apples left.
1 Bag + 36 fruits → 3 Boxes
1 Bag → 3 Boxes - 36 fruits
(x 3)
3 Bags → 9 Boxes - 108 fruits......................(Row 2)

3 Bags = 3 Bags
Row 2 = Row 1
3 Bags → 9 Boxes - 108 fruits → 130 fruits - 5 Boxes

9 Boxes - 108 fruits → 130 fruits - 5 Boxes

Add 5 Boxes to both sides of the equation
14 Boxes - 108 fruits → 130 fruits - 0 Box

Add 108 fruits to both sides of the equation
14 Boxes - 0 fruit → 238 fruits - 0 Box

14 Boxes → 238 fruits
1 Box → 17 fruits
3 Boxes → 51 fruits

(From above)
1 Bag → 3 Boxes - 36 fruits
1 Bag → 51 fruits - 36 fruits = 15 fruits

She had 1 Bag and 3 Boxes of fruits left

She had 15 fruits + 51 fruits = 66 fruits left

Hope this helps.

Cheers

speedmaths.com

PS.
Parents who wish to know more about the Advanced Model Method can check out our thread in the Happenings forum.

.

:thankyou: speedmaths.com for providing alternative way to work out the solution! Thanks once again !

[2632parent]

Good morning, really need help on this simple question? I just cannot get the answer -25m.


1) Sam and Jedi took part in a 100m race. When Sam had run 80m, Jedi only managed to run 60m. How far was Jedi from the finishing line when Sam just dashed through it?

Many thanks

[sunnymoon]

http://i49.tinypic.com/1z215kj.jpg\">

Hi, can someone help me with this question.
Thankq.
The manager of a hotel has a big hall which can be partitioned into smaller
rectangular halls. The partitions available are shown as dotted lines in the fig below.How many different types of rectangular halls can he rent out ?

can you tell me how to attach a picture? thanks

[2DMommy]

Please help me with these two questions :


1) Pasqual, Quincy , Robert and Sheridan had a total of 242 muffins. Each of them would have an equal number of muffins if Pasqual bought 10 more muffins, Quincy gave away 21 muffins, Robert increased the number of muffins he had by 2/3 and Sheridan decreased the number of muffins he had by 20%. How many muffins did each of them have ?

2) 0.6 of Luqman’s allowance is twice as much as 10% of Zachary’s allowance. After Luqman’s spends thrice as much as Zachary, Luqman’s and Zachary left with $36 and $252 respectively. How much does Zachary and Luqman’s each have at first?

Thank you.

[mom-of-2 0]

Hi, would appreciate help with this sum :


Raju took 8 hours to drive from town X to town Y. Robert who started at the same time as Raju took 6 hours to drive from town Y RI town X. When they meet each other , they were 56 km away from the midpoint of town X and town Y. What was Raju’s average speed ?

Thank you in advance !

[nounou]

Can some please help to do this Q? :imdrowning:

:thankyou: :thankyou:

Car A and Car B left Town Y at the same time, heading in the opposite direction. Car A headed for Town Z while CAr B left for Town X. The speed of Car B was 20km/h faster than Car A. After 1/2 h, Car A had completed 2/3 of its journey while Car B had completed 1/2 of its journey. The two cars were also 110km apart.
a) Calculate the speed of Car A
b) How far was Car B from Town X when Car A reached its destination?
:?: :thankyou:

[whitety]

MathIzzzFun:

whitety:

Hi, need help on these 2 qns.


1) George and Hamid drove at constant speeds from City A to City B. They started their journey at the same time. When George completed 3/4 of the journey, Hamid was 18km behind George. George reached City B 20min before Hamid. Find Hamid's speed in km/h.

2) in a bag, the ratio of the number of $2 notes to the number of $10 notes was 2:5. Ten $10 notes were removed from the bag to exchange for $2 notes which were then put back into the bag. The total value of money in the bag was unchanged after the exchange. The ratio of the number of $2 notes to the number of $10 notes then became 11:5. What was the difference between the value of the $10 notes and $2 notes after the exchange?

Thanks!

1) George completed 3/4 of journey, Hamid 18km behind
So, when George completed the journey (4/4), Hamid will be 24km behind
Hamid's speed = 24km/20 x 60 km/h = 72 km/h

2) 10 x $10 = 50 x $2
At first, number of $2 notes: $10 notes --> 2u : 5u
In the end, number of $2 notes: $10 notes --> 2u+50 : 5u-10 = 11 : 5

cross multiply/equalize:
10u + 250 = 55u - 110
1u --> 8 .. can you continue from here ?

difference in value = $168 ($10 --> $300, $2--> $132)

cheers.

:boogie: :thankyou: :boogie:

[MathIzzzFun]

2632parent:

Good morning, really need help on this simple question? I just cannot get the answer -25m.


1) Sam and Jedi took part in a 100m race. When Sam had run 80m, Jedi only managed to run 60m. How far was Jedi from the finishing line when Sam just dashed through it?

Many thanks

Distance run by
Sam : Jedi --> 80 : 60 = 4:3 = 100: 75
100m - 75 m = 25m --> Jedi would be 25m behind

cheers.