Q&A - PSLE Math

[LiteracyICare]

Thank you much! Appreciate your effort. I’ve checked the links… what I was looking for was practice papers. Yes, I guess the best would still be to go to popular and look for the book.


Thank you once again though!

[mrswongtuition]

chrisu:

This question is from the school Maths Workbook and only 4 students got the answer right. The rest mainly got the other answer. Here is the question;


Q11) Adam and Rahmad shared some beads. If Adam gave 1/3 of his share to Rahmad, Rahmad would have 70 more than Adam. If Adam gave 1/5 of his share to Rahmad, Rahmad would have 10 more than Adam. How many beads does Adam have at first?

Thank you.

If Adam gave 1/3 of his share to Rahmad...

A [----][----]
R [----][----][ 70 ]

Which means that Adam will have 2 units left while Rahmad will have 2 units plus 70 more.
Adam would have a total of 3 units at first.

If Adam gave 1/5 of his share to Rahmad....

A [--][--][--][--]
R [--][--][--][--][ 10]

Which means that Adam will have 4 units (different from the first model) left while Rahmad will have 4 units plus 10 more.
Adam would have a total of 5 units at first.

BASED ON SAME TOTAL for Adam (3 x 5 = total 15 units),
We can change the units into....

If Adam gave 1/3 of his share to Rahmad...
All units multiply by 5 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][ 70 ]

If Adam gave 1/5 of his share to Rahmad....
All units multiply by 3 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][-][-][ 10]

Comparing the above 2 models, we can see that 4 units = 70 - 10 = 60

1 unit = 60/4 = 15
15 units = 15 x 15 = 225

***
What answer did the teacher give??

[tianzhu]

Hi LiteracyICare


You’re welcome.

Best wishes

[chrisu]

Thanks Mrs.Wong, the answer given by teacher is 450. It’s before giving the 1/3 or 1/5 to Rahmad.

[mrswongtuition]

I've shared some resources you can use for foundation subjects on this thread: http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=16638&start=10

[mrswongtuition]

I think the teacher got 450 because....


From this onwards:
BASED ON SAME TOTAL for Adam (3 x 5 = total 15 units),
We can change the units into....

If Adam gave 1/3 of his share to Rahmad...
All units multiply by 5 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][ 70 ]

If Adam gave 1/5 of his share to Rahmad....
All units multiply by 3 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][-][-][ 10]

Comparing the above 2 models, the teacher compared as 2 units = 70 - 10 = 60
2 units = 60/2 = 30
15 units = 20 x 15 = 450

Regards,
Mrs Wong
Tuition Web: http://www.mwtuition.com.sg
Personal Blog: thelittleonesinmylife.blogspot.com

[Brenda10]

Brenda10:

Hi Chrisu


DD is also using MyPals workbook. Not sure whether has she attempt to this question or else ask her to give a try.

Hi Chrisu

DD said she had done this question.

1/3 - 1/5 = 2/15
70-10 = 60
60/2= 30
30 x 15 = 450

Thank you

[mrswongtuition]

Brenda10:

Brenda10:

Hi Chrisu


DD is also using MyPals workbook. Not sure whether has she attempt to this question or else ask her to give a try.

Hi Chrisu

DD said she had done this question.

1/3 - 1/5 = 2/15
70-10 = 60
60/2= 30
30 x 15 = 450

Thank you

I think this method forgot to take into consideration that though in the 2nd scenario Adam gave lesser to Rahman (by 2/15), it does not mean that 70 - 10 = 2/15 of what Adam has. Because the difference was GIVEN to Rahman and part of what Rahman has now, not totally lost of given away to others.

I'm not too sure how to explain in words, but take a look at the model I've posted and compare from there

[Sun_2010]

:?


Did anyone try working back?
If Adam had 450, then how much did Rahmad have ?
Based on the first case , Rahmad initially had 220.

But then it will not fit the case 2 scenario.

I am not very good with this method, but I can see one error

1/3 - 1/5 = 2/15 ----a
70-10 = 60
60/2= 30 ----b

a=b
hence 2/15 units = 30
adam = 225

[tianzhu]

mrswongtuition:

I think the teacher got 450 because....


From this onwards:
BASED ON SAME TOTAL for Adam (3 x 5 = total 15 units),
We can change the units into....

If Adam gave 1/3 of his share to Rahmad...
All units multiply by 5 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][ 70 ]

If Adam gave 1/5 of his share to Rahmad....
All units multiply by 3 to get a total of 15 units at first:

A [-][-][-][-][-][-][-][-][-][-][-][-]
R [-][-][-][-][-][-][-][-][-][-][-][-][ 10]

Comparing the above 2 models, the teacher compared as 2 units = 70 - 10 = 60
2 units = 60/2 = 30
15 units = 20 x 15 = 450

Regards,
Mrs Wong
Tuition Web: http://www.mwtuition.com.sg
Personal Blog: thelittleonesinmylife.blogspot.com

Hi Mrs Wong

I think your first solution is correct.

The answer is 225.

Best wishes