Q&A - PSLE Math

[Mary Joy]

tianzhu:

Mary Joy:

hello thanks for your explanation but I do not understand the sequence: 1 unit +1 unit+5.can you explain it to me?

Hi

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7399/8720130222_21d0453760_z.jpg\">

Hello :thankyou: so much for your detailed diagram and explanation.Now I understand how to do this sum

[starfish53]

:thankyou: Can anyone help me with the following question?


In a party, there are 28 boys. 3/5 of the girls at the party wear spectacles. If 1/4 of children at the party are girls who wear spectacles, how many children are there altogether at the party?

Thanks in advance.

[tianzhu]

starfish53:

:thankyou: Can anyone help me with the following question?


In a party, there are 28 boys. 3/5 of the girls at the party wear spectacles. If 1/4 of children at the party are girls who wear spectacles, how many children are there altogether at the party?

Thanks in advance.

Hi

A neat way is to use MD.

Draw a bar, divide into 4 equal parts.

Shade the first part red to show 1/4 of children at the party who are girls wearing spectacles Further subdivide it into 3 smaller units to show 3/5 of the girls at the party wearing spectacles.

The next 2 smaller units show girls not wearing spectacles. The remaining 7 smaller units show the 28 boys.

This gives 1 unit ------ 4

Total number of children ------- 12 units ------- 12*4 ------- 48

Best wishes

[YumYum]

Hi, can someone pls help with these Qns:


1) Mary bought some red marbles and have half to Noel.
Noel bought some blue marbles and gave half to Mary.
Mary lost 16 red marbles and Noel lost 55 blue marbles.
The ratio of Mary’s red marbles to blue marbles became 18:55 and the ratio of Noel’s red marbles to blue marbles became 7:20.
How many red marbles did Mary buy?

2) Container A and B contained some sand.
If 626 5/8 g (six hundred and twenty six & 5/8th g) of the sand is removed from container A, the mass of the sand in container A will be 25% that of the sand in container B.
If 179g of the sand is removed from container B, the mass of the sand in container B will be 58 1/3% (fifty eight and 1/3%) that of the sand in container A.
What is the mass of the sand in container A?

3)There were 846 glasses in a basket. Some of the glasses were found to be broken and thrown away. Of the remainder, 2/3 of the glasses were sold and 1/4 of the glasses was given away. There were 56 glasses left.
a) how many glasses were sold?
b) What fraction of the glasses in the basket was thrown away?

thanks, thanks!

[KP2]

Hi,

Could you please help me with this question?

Mr Johnson bought 1.5 times as many toy cars as toy trains. He spent $8456 altogether. A toy train costs $16 more than a toy car. The total cost of the toy trains was $616 less than the total cost of the toy cars. Find the cost of the toy car.

[PapayaDad]

3)There were 846 glasses in a basket. Some of the glasses were found to be broken and thrown away. Of the remainder, 2/3 of the glasses were sold and 1/4 of the glasses was given away. There were 56 glasses left.

a) how many glasses were sold?
b) What fraction of the glasses in the basket was thrown away?

remainder = 12u
sold = 8u
given away = 3u

12u-8u-3u=1u=56
sold = 8u = 8 x 56 = 448

remainder = 12u = 12 x 56 = 672
thrown away = 846 + 672 = 174
fraction thrown away = 174/846

PS…thanks for the correction mathizzfun…will leave this to the experts…cheers.

[cimman]

ozora:

Need guide to solve the following questions.

q1. in 20 years time, Tom's age will be 34 less than twice Joan's age.
If Joan is now 3 times older than Tom, what is Tom's present age?

q2. A is the oldest among three people. When B's age was twice of C's age, A was 30 years old. When A's age was twice of B's age, C was 21 years old. How old was C when A was 62 years old.


the above questions, I have used models to get the answers as follows: Q1 . Tom (1 unit+20years)
Joan( 4unit +20 years) x 2
Tom is 2 years

q2. B (2 units +a)
C (1 unit +a)
A( 2units +a) x 2
therefore C was 35

Besides using models, any other alternative ways to solve the above methods?
thanks

if you're willing to consider algebra, there is an alternative method. It is an approach that you can use to solve both problems. Let me know if you're interested. btw, I believe there's a typo in your 1st question.

[ozora]

cimman:

ozora:

Need guide to solve the following questions.

q1. in 20 years time, Tom's age will be 34 years less than twice Joan's age.
If Joan is now 3 times older than Tom, what is Tom's present age?

q2. A is the oldest among three people. When B's age was twice of C's age, A was 30 years old. When A's age was twice of B's age, C was 21 years old. How old was C when A was 62 years old.


the above questions, I have used models to get the answers as follows: Q1 . Tom (1 unit+20years)
Joan( 4unit +20 years) x 2
Tom is 2 years

q2. B (2 units +a)
C (1 unit +a)
A( 2units +a) x 2
therefore C was 35

Besides using models, any other alternative ways to solve the above methods?
thanks

if you're willing to consider algebra, there is an alternative method. It is an approach that you can use to solve both problems. Let me know if you're interested. btw, I believe there's a typo in your 1st question.

Hi Cimman, thanks for note. I missed out the word \"years\".:)
Besides the algebra, is it possible to use units transfer method? I wouldn't mind learning algebra as well.

[ozora]

Need guide in the following double if questions.

Q1. A team of students calculated their average score for their tests.
If anyone of them scored 5 points less, their average score would be 87.
If anyone of them scored 13 more points, their average score would be 90.
How many students are there?

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Q2. A baker made some cookies.
If he packs a vanilla cookie with a choco cookie, there will be 60 choco cookies left.
If he packs every 2 vanilla cookies with 3 choco cookies, there will be 50 vanilla cookies left.
how many cookies did he make? http://i41.tinypic.com/a28azb.jpg\">

I have used models to solve it. But i was hoping anyone could guide me to solve the above questions using units transfer method.
thanks

[PapayaDad]

Need guide to solve the following questions.

q1. in 20 years time, Tom’s age will be 34 years less than twice Joan’s age.
If Joan is now 3 times older than Tom, what is Tom’s present age?

q2. A is the oldest among three people. When B’s age was twice of C’s age, A was 30 years old. When A’s age was twice of B’s age, C was 21 years old. How old was C when A was 62 years old.


the above questions, I have used models to get the answers as follows: Q1 . Tom (1 unit+20years)
Joan( 4unit +20 years) x 2
Tom is 2 years

Sorry, but answer not correct leh.
now Tom is 2, 20 years he is 22
22 + 34 = 56
J = 56/2 = 28
now J is 28 -20 = 8
now Tom = 2
Joan is now 3 times older than Tom…not true
Joan is now 4 times older than Tom… typo? cuz ur method use 4 units…