Q&A - PSLE Math

[tianzhu]

Hi


Here’s the pictorial representation of the solution I posted last night.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7055/6787700290_3c89dbe496_z.jpg\">

[pixiedust]

Thank you tianzhu and MathIzzzFun.


Tianzhu, your lovely illustrations brighten up my morning so much ! Thank you for the efforts. I am digesting the solution…the colour-coded diagram really helps ! My heartful thanks !

[tianzhu]

homeworkmummy:

Could you pls advise if this can be solved by model method. My DD was confused with the percentage method.

Hi

It’s possible to provide graphical representations of the information in the question.

Perhaps you may want to check with your DD.

What is confusing her?

What is her understanding of percentages after reading her textbooks?

What is her understanding on comparing two quantities of percentages?

Percentages is first started in P5 Maths.Maybe, she is confused because her teacher has not covered the topic in Percentages for her P6 syllabus yet.

Best wishes

[2DMommy]

Please help me with this question :


1)On Tree-planting day, 40 pupils planted some trees. Each boy planted 3 trees and each girl planted 2 trees. The boys planted 30 more trees than the girls. How many boys were there ?

2)Box A contains 50cents and Box B contains 20cents coins. There are 19 more coins in Box B than in Box A. But the amount of money in Box A is $1.30 more than the amount of money in Box B. How much money is in Box A.

Thank you !

[MathIzzzFun]

2DMommy:

Please help me with this question :


1)On Tree-planting day, 40 pupils planted some trees. Each boy planted 3 trees and each girl planted 2 trees. The boys planted 30 more trees than the girls. How many boys were there ?

2)Box A contains 50cents and Box B contains 20cents coins. There are 19 more coins in Box B than in Box A. But the amount of money in Box A is $1.30 more than the amount of money in Box B. How much money is in Box A.

Thank you !

Hi

I will use a new approach for Q1.

Make the number of trees planted by boys and girls the same --> add 30 trees for the girls ie add 15 girls, so total number of pupils becomes 40 + 15 = 55

ratio of trees planted by boys : trees planted by girls
= 3 : 2 --> number of boys : number of girls = 2u : 3u --> total 5u

5u --> 55, 1u --> 11
Number of boys = 2 x 11 = 22, number of girls = 40 - 22 = 18

Q2.
Apply the same approach as in Q1 --> make number of coins the same ie add 19 coins to Box A, so we added 19 x $0.50 = $9.50 to Box A.

Box A will then have $9.50 + $ 1.30 = $10.80 more than Box B.

$0.50-$0.20 = $0.30

Number of coins in Box B = $ 10.80 / $0.30 = 36
Number of coins in Box A = 36 - 19 = 17
Amount of money in Box A = 17 X $0.50 = $8.50

cheers.

[2DMommy]

MathIzzzFun:

2DMommy:

Please help me with this question :


1)On Tree-planting day, 40 pupils planted some trees. Each boy planted 3 trees and each girl planted 2 trees. The boys planted 30 more trees than the girls. How many boys were there ?

2)Box A contains 50cents and Box B contains 20cents coins. There are 19 more coins in Box B than in Box A. But the amount of money in Box A is $1.30 more than the amount of money in Box B. How much money is in Box A.

Thank you !

Hi

I will use a new approach for Q1.

Make the number of trees planted by boys and girls the same --> add 30 trees for the girls ie add 15 girls, so total number of pupils becomes 40 + 15 = 55

ratio of trees planted by boys : trees planted by girls
= 3 : 2 --> number of boys : number of girls = 2u : 3u --> total 5u

5u --> 55, 1u --> 11
Number of boys = 2 x 11 = 22, number of girls = 40 - 22 = 18

Q2.
Apply the same approach as in Q1 --> make number of coins the same ie add 19 coins to Box A, so we added 19 x $0.50 = $9.50 to Box A.

Box A will then have $9.50 + $ 1.30 = $10.80 more than Box B.

$0.50-$0.20 = $0.30

Number of coins in Box B = $ 10.80 / $0.30 = 36
Number of coins in Box A = 36 - 19 = 17
Amount of money in Box A = 17 X $0.50 = $8.50

cheers.

We tried solving them using guess and check method but thought it will be tedious if numbers became too big. Many thanks for your simple and clear explaination :thankyou: !

[Superbugs]

mathfreak:

Superbugs:

Nan Hua CA1 P6 2011

Q15
A farm has some ducks and cows.
The ratio of the number of animals to the total number of legs is 8:23.
Express the number of ducks as a fraction of the cows.
Give your answer in the simplest form.
Pls assist with this question. Tks

Solution:
Pairing a cow and a duck, the two animals have 6 legs.
Hence in a situation where there are equal numbers of cows and ducks, the ratio is 2 : 6 = 8 : 24.
However, the ratio is now 8 : 23.
The difference in legs is 24-23=1 unit. Since the difference in number of legs between a cow and a duck is 2, we let 1 unit be 2 legs. By this assumption, the total number of animals is 16.
If we decrease 1 cow and increase 1 duck, the number of legs decreases by 2.
Hence, there are 7 cows and 9 ducks.
Ans: 9/7 = 1 2/7

I am rather confused by the solution. Why 24-23 becomes 1u? Why
1u=2legs? Thereafter I am lost! Pls help! Tks

[Superbugs]

Aitong CA1 2011 P6

Q5.
10/11 kg of sugar is packed into little bags. If each bag can contain only 1/7kg of sugar, how much sugar is left unpacked?
(Give your answer as a fraction in the simplest form)

10/11 divided by 1/7
I get 6 4/11
Why is the answer 4/77kg and not 4/11kg?

[MathIzzzFun]

Superbugs:

Aitong CA1 2011 P6

Q5.
10/11 kg of sugar is packed into little bags. If each bag can contain only 1/7kg of sugar, how much sugar is left unpacked?
(Give your answer as a fraction in the simplest form)

10/11 divided by 1/7
I get 6 4/11
Why is the answer 4/77kg and not 4/11kg?

Hi

4/11 is the remainder, so the answer is 4/11 of 1/7 kg = 4/77 kg.

cheers.

[small]

Superbugs:

Aitong CA1 2011 P6

Q5.
10/11 kg of sugar is packed into little bags. If each bag can contain only 1/7kg of sugar, how much sugar is left unpacked?
(Give your answer as a fraction in the simplest form)

10/11 divided by 1/7
I get 6 4/11
Why is the answer 4/77kg and not 4/11kg?

Hi Superbugs,

HTH..

6 bags of 1/7 kg ---6 x 1/7 = 6/7 or 66/77

10/11 - 66/77 --- 70/77 - 66/77 = 4/77