Q&A - PSLE Math

[tianzhu]

jonaandr:

1. Roy,Sam and Ted had a sum of money. Roy had 80% of Sam's money. Sam had 60% of Ted's. After Roy gave $12 to sam, he had 5/7 of what Sam had. How much more money did Ted have than Sam in the end?

Hi

This question has been discussed before.

It’s helpful to draw some simple pictorial representation to show the relationships among the three people.

Consider Roy and Sam first

In the beginning

Roy had 80% of Sam's money.

Roy ----- 4 units ----- 16 units
Sam ----- 5 units ----- 20 units
Total ----- 9 units ----- 36 units

After the transfer of $12 from Roy to Sam.

Roy ----- 5 units ----- 15 units
Sam ----- 7 units ----- 21 units
Total ----- 12 units ----- 36 units

A common multiple is 36.Make the total number of units the same as the amount of money(Roy and Sam) stays the same.

1 unit ---- 12

At first, Sam had (20*12) or 240

60% ----- 240
100% ----- 400

At first, Ted had 400.

In the end Sam had (21*12) or 252

Ted's amount of money stays the same before and after.

Hence, Ted had (400-252) or 148 more than Sam in the end.

Best wishes

[2632parent]

Help! Help! Have 2 questions not able to solve.


1) There were 1000 students at the parade ground and indoor sports hall. 40% of the 600 students at the parade ground were girls. 60% of the students at the indoor sports hall were girls. After some students in both venues moved from one venues to the other, 30% of the students in the parade ground and 70% of the students at the indoor sports hall were girls. How many students were there in the indoor sports hall after the movement had taken place?


2) A large warehouse had a total of 2180 black, red and white T-shirts for sale. The ratio of the number of black T-shirt to the the number of red T-shirt was 3:1. After 2/5 of the black T-shirts, 1/3 of the white T-shirts and none of the red T-shirts were sold on the first day, there were 1504 T-shirts left. How many red T-shirts did the warehouse have at first?


Thank you

[tianzhu]

2632parent:

1) There were 1000 students at the parade ground and indoor sports hall. 40% of the 600 students at the parade ground were girls. 60% of the students at the indoor sports hall were girls. After some students in both venues moved from one venues to the other, 30% of the students in the parade ground and 70% of the students at the indoor sports hall were girls. How many students were there in the indoor sports hall after the movement had taken place?

Hi

This question has been discussed before.

Best wishes

http://farm7.static.flickr.com/6070/6154555481_a1f43e1359_z.jpg\">

[tianzhu]

2632parent:

2) A large warehouse had a total of 2180 black, red and white T-shirts for sale. The ratio of the number of black T-shirt to the the number of red T-shirt was 3:1. After 2/5 of the black T-shirts, 1/3 of the white T-shirts and none of the red T-shirts were sold on the first day, there were 1504 T-shirts left. How many red T-shirts did the warehouse have at first?

Hi

Hope this helps.

Best wishes

http://farm7.staticflickr.com/6177/6160679750_ff917d0516_z.jpg\">

[jarenchuatw]

Another question in need help to solve:


2/3 of the fruits at a stall were oranges. 3/4 of the remaining fruits were appleas and the rest were banaanas. There were 150 more oranges than apples. After selling some apples, 10% of the remaining fruits were apples. How many apples were sold?

Thanks

[tianzhu]

jarenchuatw:

Another question in need help to solve:


2/3 of the fruits at a stall were oranges. 3/4 of the remaining fruits were appleas and the rest were banaanas. There were 150 more oranges than apples. After selling some apples, 10% of the remaining fruits were apples. How many apples were sold?

Thanks

Hi

A neat way is to use MD or you may also work with units and parts.

Draw a long bar and divide into 3 equal parts.

Further divide each part into 4 smaller units.

8 units ------- oranges
3 units ------ apples
1 unit ------- banana

8 - 3 ------ 5

5 units ------ 150

1 unit ------ 30

Oranges ------- 240

Apples ------- 90

Banana -------- 30

Let’s represent the remaining number of apple sold as A

A -------- 1p

270 +A -------- 10p

Equalize the parts

10A -------- 10p

270 + A -------- 10A

9A ------- 270

A -------- 30

Number of apples sold -------- 90 – 30 -------60

Best wishes

[Shimmer]

Need help on this question.


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.

[pixiedust]

Shimmer:

Need help on this question.


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.

Total spent $21.60
Spent on notebooks -> $9.60+$2.40= $12
Spent on pencils -> $9.60

#pencils -> 4u
#notebooks -> 1u

1u notebook -> $12
1u pencils -> $9.60/4= $2.40

($12-$2.40) / 3.20 = 3 -> Hence, he bought 3 notebooks.
Therefore, he bought 12 pencils.
12 pencils -> $9.60
1 pencil -> $0.80

[2632parent]

Councillor Thanks for the solution but I have problem understanding how you get

2u + 2(676) ----- 1504

[tianzhu]

2632parent:

Councillor Thanks for the solution but I have problem understanding how you get

2u + 2(676) ----- 1504

Hi

14 units + 2 parts ------- 1504

2 units + (12 units + 2 parts) ------- 1504

2 units + (6 units + 1 part) + (6 units + 1 part) ------- 1504

6 units + 1 part ----- 676

Hence, 2 units + 2(676) ------- 1504

Best wishes