Q&A - P5 Math

[MathIzzzFun]

ajmum:

Thanks charsen .


Need help for another 2 questions,

1. There are some crystal and glass marbles in a pouch. If 3 crystal marbles are removed from the pouch, the number of crystal marbles left will be 1/6 of the glass marbles left. If 5 glass marbles are removed from pouch, the number of crystal marbles left will be 1/4 of the glass marbles left. How many marbles are there in the pouch at first.

Thank you for help.

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cheers.

[MathIzzzFun]

bookwormkids:

Hi, need some help.


P5 SA2 2007 Ai Tong
Q42
Bobby, Edward and Kelvin made a bottle of paper stars. The number of paper stars Bobby made was 21 more than 1/4 the total number of paper stars in the bottle. The number of paper stars Edward made was 30 more than 1/4 of the remaining number of paper stars in the bottle. Kelvin made the remaining 114 paper stars. How many paper stars did they make in all?


Thanks!

Q42.
Work backwards

It would be good to draw a simple diagram or model - I will not put up one here due to time constraint.

Total = Bobby's stars + Remainder 1 --- Bobby's stars = 1/4 Total + 21
Remainder 1 = Edward's stars + Remainder 2 --- Edward's stars = 1/4 of Remainder 1 + 30
Remainder 2 = Kelvin's stars = 114

Remainder 1 = Edward's stars + 114 = 1/4 of Remainder 1 + 30 + 114
3/4 Remainder 1 = 144
Remainder 1 --> 144/3 x 4 = 192

Total = Bobby's stars + Remainder 1 = 1/4 Total + 21 + 192
3/4 Total = 213
Total --> 213/3 x 4 = 284

They made 284 altogether.

cheers.

[MathIzzzFun]

bookwormkids:

Hi, need some help.


P5 SA2 2007 Ai Tong
Q43
A, B and C are three numbers. The average of A, B and C is 5 greater than the average of A and B. If C is 38, find the total of A, B and C.


Thanks!

http://i50.tinypic.com/35d68mq.jpg\">

cheers.

[MathIzzzFun]

bookwormkids:

Hi, need some help.


P5 SA2 2009 Ai Tong
Q12
Siti had some money. She gave some money to Kelly and Lindy and saved the rest. The ratio of her savings to the amount she gave away was 5: 8. The ratio of Kelly's money to Lindy's money was 5: 3 at first. After Kelly's money increased by $128 and Lindy's money decreased by $128, the ratio of Kelly's money to Lindy's money became 3: 1. How much money did Siti save?

Thanks!

Siti's savings : Kelly's money : Lindy's money
--> 5u: 5u : 3u

After Kelly's money increased by $128 & Lindy's money decreased by $128
Kelly's money : Lindy's money --> 5u + $128 : 3u - $128 = 3 : 1

Equalize/cross-multiply:
5u + $128 = 9u - $384
1u --> $128

Siti saved --> 5 x $128 = $640

cheers.

[bookwormkids]

Hi enreachlearningcentre & MathIzzzFun!


Thank you for your help!

[happyheart]

Can someone help to explain the concept of <No x value and inverse proportion>? Below are 2 similar type questions based on the concept. Thanks in advance.



Q1) A group of children was given 136 candies on Children’s Day. Each girl received 3 candies and each boy received 4 candies. There were 6 more boys than girls in the group. How many girls were there in the group?


Q2) A group of children was given some candies on Children’s Day. Each girl received 3 candies and each boy received 5 candies. There were 3/4 as many boys as girls in the group. If the boys received 60 sweets more than the girls, how many girls were there in the group?

[tianzhu]

happyheart:

Q1) A group of children was given 136 candies on Children's Day. Each girl received 3 candies and each boy received 4 candies. There were 6 more boys than girls in the group. How many girls were there in the group?

Hi

Good Morning.

You may use the “Grouping concept”

Each girl ------ 3 candies

Each boy ------ 4 candies

There were 6 more boys than girls in the group.

6*4 ------ 24

136 - 24 ------- 112

Consider a group of 1 boy and 1 girl.

1 boy + 1 girl ------- 7 candies

112/7 ------ 16

There were 16 groups.

Number of girls ------ 16

Number of boys ------- 16 + 6 ------ 22

Best wishes

[tianzhu]

happyheart:

Q2) A group of children was given some candies on Children's Day. Each girl received 3 candies and each boy received 5 candies. There were 3/4 as many boys as girls in the group. If the boys received 60 sweets more than the girls, how many girls were there in the group?

Hi

Boy ------- 3 units

Girls ------ 4 units

Using the concept of “Number*Value”, you may tabulate it if you prefer.

Boy ------- 3*5 -------- 15 units

Girl ------- 4*3 -------- 12 units

15 – 12 ------- 3

3 units -------- 60

1 unit ------- 20

Number of girls -------- 4*20 -------- 80

Check

Number of sweets received by boys -------- 60*5 ------- 300

Number of sweets received by girls -------- 80*3 ------- 240

Difference ------- 300 – 240 ------- 60

Best wishes

[happyheart]

tianzhu:

happyheart:

Q2) A group of children was given some candies on Children's Day. Each girl received 3 candies and each boy received 5 candies. There were 3/4 as many boys as girls in the group. If the boys received 60 sweets more than the girls, how many girls were there in the group?

Hi

Boy ------- 3 units

Girls ------ 4 units

Using the concept of “Number*Value”, you may tabulate it if you prefer.

Boy ------- 3*5 -------- 15 units

Girl ------- 4*3 -------- 12 units

15 – 12 ------- 3

3 units -------- 60

1 unit ------- 20

Number of girls -------- 4*20 -------- 80

Check

Number of sweets received by boys -------- 60*5 ------- 300

Number of sweets received by girls -------- 80*3 ------- 240

Difference ------- 300 – 240 ------- 60

Best wishes

Thank you, Tianzhu.

[Udon]

Hi hi...seek help for better solution...


Q1. Maria spent $480 on food and 25% of her money on clothes and had $1020 left. What percentage of her money did she spend?


$480+$1020=100%-25%
$1500=75%
1%=1500/75
1%=20

25%=25x20=$500

$1500+$500=$2000

480/2000*100=24%

24%+25%=49%

Total % spent 49%

was this solution too long winded? Please assist.
Thank you.