Q&A - PSLE Math

[youngtay]

Hi, Pls help


The ratio of the number of stickers Alex had to the number of stickers Beng Han had was 1:3. After each of them received 25 stikers, the ratio became 3:4. How many stickers did they have altogether at first?

TIA

[Brenda10]

youngtay:

Hi, Pls help


The ratio of the number of stickers Alex had to the number of stickers Beng Han had was 1:3. After each of them received 25 stikers, the ratio became 3:4. How many stickers did they have altogether at first?

TIA

Hi, dd working:

A:B

1 : 3 (at First, the different is 2)
+25 +25 (Recd)
3 : 4 (after, the different is 1)

A:B
1:3 (x1)
6:8 (x2)
----
5:5

5u=25
1u=5

4u x 5 = 20 stickers

They have 20 stickers at first

Thank you

[youngtay]

Brenda10


Thanks

[tianzhu]

Hi


Some interesting questions from onsponge.

1)Mrs Lim bought some bowls and plates. If she buys another 5 bowls, there are 60% as many bowls as plates. If she buys another 9 plates, there will be thrice as many plates as bowls. How many bowls did she buy? ( P5 Catholic High School Math,SA2,2009)

2)If Ahmad gives Pillay 17 marbles, the ratio of his marbles to that of Pillay’s will be 4:7. If Ahmad gives Pillay 5 marbles, both will have the same number of marbles. How many marbles does Ahmad have? ( Singapore Chinese Girls’ School P6 2010 SA1 Maths Q10)

3)Ben and Marcus received some money from their mother. Marcus would have $64 more than Ben if Ben gave 2/5 of his share to Marcus. Marcus would have $144 more than Ben if Ben gave 2/3 of his share to Marcus. How much money did Ben receive from his mother? (Singapore Chinese Girls’ School P6 2010 SA1 Maths Q13)

Best wishes

[tianzhu]

Hi


Another interesting question from onsponge, students who are more mathematically inclined often solve such questions using simultaneously equations as they are two unknowns and two equations.

For the benefits of future PSLE students,how about coming up with some strategies(heuristics taught in primary schools) to teach students cope with such questions?

Let us make this a uniquely KSP experience, active participation from members is strongly encouraged.

There were 32 tourists on a bus. 2/5 of the men and 1/4 of the women were from Singapore. The total number of tourists who came from Singapore was 11. How many men came from Singapore?( P6 Nan Hua CA1 2010 P2 Q11)

Best wishes

[Brenda10]

tianzhu:

Hi


Another interesting question from onsponge, students who are more mathematically inclined often solve such questions using simultaneously equations as they are two unknowns and two equations.

For the benefits of future PSLE students,how about coming up with some strategies(heuristics taught in primary schools) to teach students cope with such questions?

Let us make this a uniquely KSP experience, active participation from members is strongly encouraged.

There were 32 tourists on a bus. 2/5 of the men and 1/4 of the women were from Singapore. The total number of tourists who came from Singapore was 11. How many men came from Singapore?( P6 Nan Hua CA1 2010 P2 Q11)

Best wishes

Hi Tianzhu

Thank you for your highlight.

DD had done this question using branching method and her working was as follow:

Total : 32 u

Men : 20u, therefore 8u (Singapore), 12 u (others)
women: 12u, therefore 3u (Singapore), 9u (others)

She then derive the answer of 8u = 8 men from Singapore

Her answer was same with the answer sheet and hopefully her working was correct.

Thank you

[Suz855]

What about using the unit method\t


Men Women
tourist\t5\t4\ttotal = 32
Sg\t2\t1\ttotal = 11\tx4
\t8\t4 total = 44

Since the number of women or men tourist are fixed, we can find the CM for either of them. In this case, since we have, 4 and 1 for women, we can simply multiply the later by 4

Doing a simple comparison, the extra 3u of men –> 44-32=12
Since question ask for how many tourist are men, we can easily solve by
12/3 x 2 = 8

[tianzhu]

Hi Brenda10 and Suz855


Thank you for your response. I am sure future PSLE students will benefit from your sharing.

Best wishes.

[tianzhu]

Brenda10:

DD had done this question using branching method and her working was as follow:

Total : 32 u

Men : 20u, therefore 8u (Singapore), 12 u (others)
women: 12u, therefore 3u (Singapore), 9u (others)

Hi Brenda10

I’ll be helpful if you could elaborate more on how you arrive at 20u,8u and 12u for men and 12u,3u and 9u for women using the Branching method.

Do you use Guess and Check to arrive at the numbers?

Best wishes

[Brenda10]

tianzhu:

Brenda10:

DD had done this question using branching method and her working was as follow:

Total : 32 u

Men : 20u, therefore 8u (Singapore), 12 u (others)
women: 12u, therefore 3u (Singapore), 9u (others)

Hi Brenda10

I’ll be helpful if you could elaborate more on how you arrive at 20u,8u and 12u for men and 12u,3u and 9u for women using the Branching method.

Do you use Guess and Check to arrive at the numbers?

Best wishes

Hi Tianzhu

I check with dd and you're right the initial 20u and 12u she was using some guessing methods.

Thank you