Q&A - P5 Math

[tianzhu]

chokos:

Qn3)
Mark's current age is 1/4 of Ronald's. In 24 years' time, Ronald age will be 14 years less than twice Mark's age. What is Ronald age now?
Model Answer: 20

Hi

Now
Mark’s age ------ 1 unit
Ronald’s age ------ 4 units

In 24 years’ time
Mark’s age ------ 1 unit + 24
Ronald’s age ------ 4 units + 24

Ronald age will be 14 years less than twice Mark's age.

You may use MD or work using units depending on your preference.

1 unit + 24 + 1 unit + 24 ------ 4 units + 24 + 14
1 unit ----- 5

4*5 ------ 20

Ronald is 20 years old now.

Best wishes

[tianzhu]

chokos:

Qn 1)
There are some crystal and glass marbles in a pouch. If 3 crystal marbles are removed from the pouch, the number of crystal marbles left will be 1/6 of the glass marbles left. If 5 glass marbles are removed from the pouch, the number of crystal marbles left will be 1/4 of the glass marbles left. How many marbles are there in the pouch at first?
Model Answer: 62.5

Hi

Based on the question as worded, the answer is 62.5.

At first
Crystal marbles ----- 1 unit + 3
Glass marbles ------ 6 units

In the end
Crystal marbles ----- 1 part
Glass marbles ------ 4 parts

Again, equalise the parts or cross multiply.

(1 unit + 3)*4 ------- 6units - 5
4 units + 12 ------- 6 units – 5

2 units ------ 17
1 unit ------ 8.5

Crystal marbles ------- 11.5
Glass marbles ------- 51
Total number of marbles -------- 62.5

Best wishes

[tianzhu]

zico:

Is there a algerbra way to solve this?

Hi

Yes, there is.

Best wishes

[2snoopy]

Is primary 5 students start to learn algebraic equation in school? If yes, then can use my method.

[chokos]

Hi all,

Thanks for helping.
I need help to solve the following questions:

Q 1) Some pupils from 5K, 5L and 5M took part in a Social Studies quiz. 34 participants were from 5L and 5M. 21 participants were not from 5L and 19 participants were not from 5M. How many pupils from these 3 classes took part in the quiz? Model Answer: 37pupils

Q 2) Mrs Lee spent ½ of her money on some almond cookies and 2/5 of the remaining money on 6 slices of butter cake. Each slice of butter cake costs thrice as much as one almond cookie. How many almond cookies did she buy? Model Answer: 18 almond cookies.

Q3) Three sisters Lisa, Ming and Nora shared the cost of a present for their father. Lisa paid ¼ of the total share of Ming and Nora. Ming paid 1/9 of the total share of Lisa and Nora. Nora paid $60 more than Ming. How much did the present cost? Model Answer: $100

Q4) Jason and Kevin were given some money each. If Jason and Kevin spent $100 and $50 each day respectively. Jason would have $1300 when Kevin had spent all his money. If Jason and Kevin spent $50 and $100 each day respectively, Jason would have $3700 when Kevin had spent all his money. How much money was given to Jason at the beginning.
Model Answer: $4500

[small]

wintay:

Can anyone help to solve the problem sum below. Thanks


6 hats and 5 belts cost $150. 5 hats and 6 belts cost $147. What is the cost of one belt?

Another way to solve this question.

Given that:
6 hats and 5 belts cost $150
5 hats and 6 belts cost $147

add togother become:
11 hats and 11 belts cost $297

divide by 11
1 hat and 1 belt cost $27

x 5
5 hats and 5 belts cost $135

Given that:
5 hats and 6 belts cost $147

1 belt ---- $147 - $135 = $12

[KSgal]

chokos:

Hi all,

Thanks for helping.
I need help to solve the following questions:

Q 1) Some pupils from 5K, 5L and 5M took part in a Social Studies quiz. 34 participants were from 5L and 5M. 21 participants were not from 5L and 19 participants were not from 5M. How many pupils from these 3 classes took part in the quiz? Model Answer: 37pupils

5L + 5M: 34

21 not from 5L means that the 21 are from 5K + 5M

19 not from 5M means that the 19 are from 5K + 5L

Notice that if you add all the numbers up, you will get 2 5K, 2 5L and 2 5M.

So:

2 5K, 2 5L, 2 5M--34+21+19=74
No. of pupils from all 3 classes (1 5K, 1 5L, 1 5M)--74/2=37

Ans: 37 pupils

Hope this helps ^_^

[KSgal]

chokos:

Q 2) Mrs Lee spent ½ of her money on some almond cookies and 2/5 of the remaining money on 6 slices of butter cake. Each slice of butter cake costs thrice as much as one almond cookie. How many almond cookies did she buy? Model Answer: 18 almond cookies.

Actually, I've got 45 for this question. Not too sure if I am correct. Here's my working:

Spent on butter cake--2/5 X 1/2(remainder) = 1/5 of total
1/5 of total worth of almond cookies--6 X 3 = 18

However, 1/2 was spent on almond cookies, not 1/5.

1/2=5/10 of total
1/5=2/10 of total

2/10--18 cookies
1/10--18/2=9 cookies
5/10--9 X 5= 45 cookies

My answer: 45 cookies

[KSgal]

chokos:

Q3) Three sisters Lisa, Ming and Nora shared the cost of a present for their father. Lisa paid ¼ of the total share of Ming and Nora. Ming paid 1/9 of the total share of Lisa and Nora. Nora paid $60 more than Ming. How much did the present cost? Model Answer: $100

1st ratio:
L: 1u x2 = 2u
M+N: 4u x2= 8u
Total: 5u x2= 10u

2nd ratio:
M: 1u
L+N: 9u
Total: 10u


Since the price of the present will not change, the total of both ratio should be the same. Thus, we x2 the total of the 1st ratio to make the total of both ratios to be the same. And since we x2 the total, we need to x2 everything else in the 1st ratio.

No. of units for Nora--9u(L+N) - 2u(L) = 7u(N)
Diff between Nora and Ming--7u-1u=6u
6u--$60
1u--$60/6=$10
10u--$10 X 10= $100

Ans: $100

[buds]

Helloooo again, tianzhu! :peekaboo:


I have a few more for you here.

I am thinking of a fraction.
The sum of its numerator and denominator is 20.
When i add 22 to its denominator, the fraction becomes 1/6.
What is the fraction i am thinking of?

This question carries 4 marks! :yikes:

Benjamin left Singapore for an 8-day exchange programme in Perth.
When he returned, he realized he had to tear off 8 pages from his day to day calendar.
The sum of all the dates on the pages he tore is 84.
On which day did he leave Singapore?

1. 5 February
2. 6 January
3. 7 June
4. 8 August

This wan 2 marks.

I suppose the task at hand is more to the issue of solving such questions
without having to spend too much time on them. When have to
think too long & too much over a few questions my DD1 gets her
usual what she calls mental block.. head jammed.. cannot think.. :slapshead: