Q&A - PSLE Math

[tianzhu]

Dazzle:

Pls help. Q 9 from MGS Prelim 2012


Bottle A and bottle B both contain some juice.
If 1.3 litre of juice was poured into bottle A, the volume of juice in A will be 1.6 times that of the volume of the juice in bottle B.
If 480 ml of juice was poured into bottle B, the volume of juice in bottle B will be 1.8 times that of the volume of the juice in bottle A.

(a) What is the volume of juice in bottle A? (Ans. 1.1 litre)
(b) what is the difference in the volume of juice in both bottles? (Ans: 0.4 litre)

Hi

This question touches on the \"double if\" scenarios.

You may use MD or UP.

The steps are rather mechanical, students need to practise to get the hang of it.

Some may use the term \"Cross multiply\" instead of \"Equalising the parts\".They serve the same purpose that is to enable you to make a comparison.

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8042/8011336725_941b3990a6_z.jpg\">

[jewelbox]

Hi, appreciate any help to solve these qns. Thanks.


1)In a sch hall, chairs were arranged in rows such that there were exactly 9 chairs in each row. For a concert, Mr ong brought 6 more chairs into the hall and rearragned all the chairs. Thee are now exactly 7 chairs in each row and 12 more rows than before. How many chairs are there in the sch hall for the concert? (PSLE qn)

2. Chairs are arranged in rows in a sch hall. There are 6 chairs left over if 13 chairs are put in each row. Hwoever, if 15 chairs are arranged in each row, there will be a shortage of 4 chairs. if the no. of people attending the concert is betw 200 and 30, find the no. of chairs in the hall.

3. When K’s age was twice Bala’s age, M’s age was 30. When M’s age was twice K’s age, Bala’s age was 21. Given that M was the olderst among the 3 persons, find B’s age when M was 62 years old. (Ans: 35)

[tianzhu]

whitety:

Hi, need help on this qn.


Lina bought some chocolate and vanilla muffins in the ratio 2:3. She packed the chocolate muffins into boxes of 3 and the vanilla muffins into boxes of 4. There were 6 more boxes of vanilla muffins than chocolate muffins. How many chocolate muffins did Lina buy?

Thanks!

Hi

2:3 ------- 24:36

This is equivalent to 8 boxes of chocolate muffins and 9 boxes of vanilla muffins.

We are looking for 6 more boxes of vanilla muffins.

Hence multiply by 6 to get 48 of chocolate muffins and 54 boxes of vanilla muffins.

Number of chocolate muffins ---------- 48*3 ------ 144

Best wishes

[tianzhu]

jewelbox:

3. When K's age was twice Bala's age, M's age was 30. When M's age was twice K's age, Bala's age was 21. Given that M was the olderst among the 3 persons, find B's age when M was 62 years old. (Ans: 35)

Hi

Please refer to this solution.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7067/6854267621_b1022b156e_z.jpg\">

[AJH]

tianzhu:

htn:

tianzhu
how to use MD to solve this q? can teach me?
TIA

Hi mumwgals and htn

MD refers to “Model Drawing” or Model Diagram”.

In this question, the units or boxes showing boys and girls in the parade ground and indoor hall are of different measures. They are not of the same sizes.

A student should note that the number of boys and girls remains the same before and after the transfer. The total number of 1000 did not change at all.

There are two unknowns with two linear equations.Recall the time at lower primary when you’re using the stars and moons, you could actually solve the equations pictorially as shown in the slide. This question is crafted in such a way that it is pretty neat to use MD.

Otherwise, students may choose to work using “Units and Parts” or letters of the alphabet as representation. Use the method you are comfortable with.

Hope this helps.

Best wishes

http://farm7.static.flickr.com/6070/6154555481_a1f43e1359_z.jpg\">

Hi - how did u get 480? I got 460. Thank u.

[jewelbox]

TianZhu, thanks for the soln on Bala's age. :thankyou:

[charsen]

[quote="jewelbox"]Hi, appreciate any help to solve these qns. Thanks.


1)In a sch hall, chairs were arranged in rows such that there were exactly 9 chairs in each row. For a concert, Mr ong brought 6 more chairs into the hall and rearragned all the chairs. Thee are now exactly 7 chairs in each row and 12 more rows than before. How many chairs are there in the sch hall for the concert? (PSLE qn)[quote]
Hi
This question has been discused in page 507.It is similar to this question.
12 new rows of 7 chairs----->84 chairs
no. of chairs removed from the original arrangement----->78 chairs
original no. of rows---->78/2=39
39x9+6=357chairs(ANS)
Cheers

[ximinful]

Hi,can someone help me with nanyang 2012 prelim q10?

Ps. I know this qns has been discussed before but I don’t understand the solution.
Tia

[whitety]

tianzhu:

whitety:

Hi, need help on this qn.


Lina bought some chocolate and vanilla muffins in the ratio 2:3. She packed the chocolate muffins into boxes of 3 and the vanilla muffins into boxes of 4. There were 6 more boxes of vanilla muffins than chocolate muffins. How many chocolate muffins did Lina buy?

Thanks!

Hi

2:3 ------- 24:36

This is equivalent to 8 boxes of chocolate muffins and 9 boxes of vanilla muffins.

We are looking for 6 more boxes of vanilla muffins.

Hence multiply by 6 to get 48 of chocolate muffins and 54 boxes of vanilla muffins.

Number of chocolate muffins ---------- 48*3 ------ 144

Best wishes

Hi tianzhu,
Thank you very much !!!

[Dazzle]

Tianzhu,

Thank you so much for your answer to Q9 of MGS Prelim 2012. Will you show how to solve with Model? Thanks again.