Q&A - PSLE Math

[Dharma]

kancheongmum:

for algebra question if the work out answer is (168 - x)/2 + x
do the student leave the answer this way or has to simplified further to
84 + 1/2 x

Hi kancheongmum,

You will need to simplify the answer to 84 + x/2

[CTong]

Pls help to solve:


James had 20 goldfishes and 30 guppies in a fish tank. 20% of the guppies died. James bought another 16 goldfishes.
a) What percentage of the fish were guppies?
b) What was the increase in percentage of goldfish?

[kancheongmum]

hi Tianzhu will ask ds to check with his teacher tomorrow.

options (1) 44 yrs old (2) 43 yrs old (3) 42 yrs old (4) 41 yrs old
tks

[Vanilla Cake]

kancheongmum:

Hi Tianzhu and Dharma

Thank you got all the info now.
one more question MCQ RV2010 Q12 (ans 43 yrs old)
The average age of Mr Lim\"s family of 4 is 26years old. The total age of Shawn and Mr Lim is 2 years more than the total age of Mary and Mrs Lim. How old is Mr Lim?

Dear Uncle Tianzhu and Uncle Dharma,

There is missing information in kancheongmum's post. There is actually a table in this question and it is stated that age of Shawn (son) -> 10 yrs old.Without this information about the age of Shawn (son), it's not possible to solve this question.

Answers option:
(1) 44 yrs old
(2) 43 yrs old
(3) 42 yrs old
(4) 41 yrs old

Suggested solution using algebra
Let the age of Mr Lim be n.
Age of Mrs Lim+Age of Mary (daughter)=10+n-2=8+n
8+n+n+10=104
2n=86
n=43

Age of Mr Lim = 43 years old
Answer option (2)

[kancheongmum]

Thank you Vanilla Cake, sorry forgot to type in Shawn’s age 10.

[Ler]

tianzhu:

Ler:

Hi VC and tianzhu

I try that VC given the solutions (for abc parents), but could not access to the link but only provided the solution

Sorry VC, i seldom use computer, only touches this week only, still learning, may VC can help me to link to it. for uncle observation solution. May be can type out the website for me. I saw him draw model , i seems to understand more..... thanks.

Hi Ler

Here’s Observer blog
http://prischoolmaths.blogspot.com/

This is another good resource for PSLE students
http://road-to-psle.blogspot.com/

Best wishes

Tianzhu, Thank you very much

[tianzhu]

Vanilla Cake:

Dear Uncle Tianzhu and Uncle Dharma,


There is missing information in kancheongmum's post. There is actually a table in this question and it is stated that age of Shawn (son) -> 10 yrs old.Without this information about the age of Shawn (son), it's not possible to solve this question.

Hi VC

Good Morning.

Thank you for giving us the number.It's the missing link to the solution.

Best wishes

[tianzhu]

kancheongmum:

Thank you Vanilla Cake, sorry forgot to type in Shawn's age 10.

Hi kancheongmum

Good Morning.

26*4 -----104

Mr Lim + Shawn ------ 53

If Shawn is 10, then Mr Lim is 43.

Best wishes

[Dharma]

The age of the Lim family:

Mr Lim = a
Mrs Lim = b
Shawn = c = 10
Mary = d

Total age = a + b + c + d = 26 x 4 = 104
(a + c ) - (b + d) = 2
(a + c - 1 ) - ( b + d + 1) = 0
(a + c - 1) = 104/2 = 52
Mr Lim’s age, a = 52 + 1 - 10 = 43

or

a + c = (104 + 2)/2 = 53
a = 53 - 10 = 43

[tianzhu]

Hi


Although the word equal is not expressly specified in the question, students should be able to achieve breakthrough with these key words same bag from the same shop. This indicates that the cost of the bag or the money spent on the bag is the same.

The equal concept compares two or more fractions, percentages, decimals or even ratios that represent equal quantities.

You may use MD or Units method to solve such questions.

In this post, I’ll be sharing the MD way. When drawing the MD, reflects on the stage where both have an equal amount.

As the question asks for the answer to be expressed in percentage, you may not need to use the value of the remaining amount of money.

I hope it helps students get a better understanding of Equal Concept.

Best wishes

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