Q&A - PSLE Math

[Shimmer]

MathIzzzFun:

Shimmer:

In the 6A and B,the total number of girls was 100% more than boys. The ratio of boy to girl in 6A is 3:4 and the ratio of boy to girl in 6B is 1:6. If there were 8 more girls in 6a than 6b, find the no. of pupils in 6a.

Hi

6A, Boys: Girls = 3:4 --> 9:12
6B, Boys: Girls = 1:6 --> 2:12

There were 8 more girls in 6A than 6B,
6A, Boys: Girls --> 9u + 6 : 12u + 8 -- total --> 21u + 14
6B, Boys: Girls --> 2u : 12u

Total number of girls was 100% more than boys,
24u + 8 = 2 x (11u +6)
1u --> 2

Total number of pupils in 6A --> 21 x 2 + 14 = 56

cheers.

Thanks so much KaisuGrandMaster !

[jonaandr]

Help needed for these 4 questions - many thanks in advance!


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?

2. 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.

3. Ms Lee baked 24 more chocolate muffins than banan muffins. After she gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins, she was left with 35 more chocolate muffins than banana muffins. How many chocolate muffins did she bake at first?

4. At first, ravi had $200 more than vincent. He gave 40% of his money to Vincent. vincent then gave 25% of his money to ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?

[tianzhu]

jonaandr:

4. At first, ravi had $200 more than vincent. He gave 40% of his money to Vincent. vincent then gave 25% of his money to ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?

Hi

You may draw MD to show the transactions or choose to work using units.

At first
Ravi ----- 20 units + 200
Vincent ------20 units

I use 20 units instead of 10 units to avoid working with decimals during future transfer.

Ravi gave 8 units + 80 to Vincent. He was left with 12 units + 120

Vincent now had 28 units + 80

Vincent then gave 25% of his money to Ravi.
25% ------- 7 units + 20

In the end
Ravi --------- 19 units + 140
Vincent ------- 21 units + 60

19 units + 140 + 68 ------ 21 units + 60
1 unit ----- 74

Vincent gave (7*74) + 20 or 538 to Ravi.

Best wishes

[tianzhu]

jonaandr:

3. Ms Lee baked 24 more chocolate muffins than banan muffins. After she gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins, she was left with 35 more chocolate muffins than banana muffins. How many chocolate muffins did she bake at first?

Hi

A common multiple of 6 and 8 is 24

At first
Banana muffins ----- 24 units
Chocolate muffins ----- 24 units + 24

She gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins

In the end
Banana muffins ----- 15 units
Chocolate muffins ----- 20 units + 20

She was left with 35 more chocolate muffins than banana muffins.

15 units + 35 ------ 20 units + 20
5 units ------ 15
1 unit ------ 3

Number of chocolate muffins at first ----- (24*3) + 24 ------ 96

Best wishes

[tianzhu]

jonaandr:

2. 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.

Hi

This question has been discussed before.

You may use MD or present your solution using Number*Value in tabulated form.

Due to time constraints, I shall give you some pointers for you to draw the MD.

Amount spent on pencils ----- (21.6 - 2.4)/2 ----- 9.6
Amount spent on note books ----- 12

9.6/4 ----- 2.4
12 – 2.4 ----- 9.6

Each notebook costs $3.2 more than a pencil.

Number of notebooks ----- 9.6/3.2 ----- 3

Number of pencils ----- 12

Cost of 1 pencil ----- 9.6/12 ------ 0.8

Best wishes

[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