Q&A - PSLE Math

[tianzhu]

Mary Joy:

Hi everyone,


Need help in solving this question.

Mr and Mrs Lim left their house at the same time but travelled in opposite directions along a straight road.Mrs Lim drove at a speed which was 10 km/h slower than Mr Lim.30 min later,when Mr Lim reached his destination,he and Mrs Lim were 85 km apart.How far did Mrs Lim travel when Mr Lim reached his destination?

Thank you

:thankyou: :lovesite:

Hi

Start with a simple diagram.

In 1h, Mrs Lim was 10 km behind Mr Lim.

In 30 minutes, Mrs. Lim was 5 km behind Mr. Lim.

1 unit + 1 unit + 5 ------ 85

1 unit ------- 40

Distance covered in 30 minutes ------- 40 km (distance travelled by Mrs Lim)

Best wishes

[Mary Joy]

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

My answer for the first question is: Tom is 2 4/5 years old,and I used the model method too :?

[Mary Joy]

tianzhu:

Mary Joy:

Hi everyone,


Need help in solving this question.

Mr and Mrs Lim left their house at the same time but travelled in opposite directions along a straight road.Mrs Lim drove at a speed which was 10 km/h slower than Mr Lim.30 min later,when Mr Lim reached his destination,he and Mrs Lim were 85 km apart.How far did Mrs Lim travel when Mr Lim reached his destination?

Thank you

:thankyou: :lovesite:

Hi

Start with
a simple diagram.

In 1h, Mrs Lim was 10 km behind Mr Lim.

In 30 minutes, Mrs. Lim was 5 km behind Mr. Lim.

1 unit + 1 unit + 5 ------ 85



1 unit ------- 40

Distance covered in 30 minutes ------- 40 km (distance travelled by Mrs Lim)

Best wishes

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

[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\">

[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.