Q&A - PSLE Math

[tianzhu]

stary:

Hi all, have a question to ask...


Two runners, Tom and Peter, were training on a 400-metres circular track. They started running in the same direction from the same place at the same time. The average speed of Tom was 1.2m/sec while Peter was running at 1.8m/sec. How long, in minutes, did Tom take to meet Peter the second time after they started running? Express your answers in a mixed fraction.

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Hi stary

Good Morning.

Your question looks a bit tricky because of the mixed fractions.

I believe many PSLE kids are familiar with questions like this.

Two runners, Mary and Jane were training on a circular track. They started running in the same direction from the same place at the same time. Mary and Jane can run around the track in 8 and 12 minutes respectively. How long, in minutes, did Mary take to meet Jane the second time after they started running?

You may use “Systematic Listing” to work it out.

For your question, I did a quick check; the answer is 22 2/9 minutes (mixed fractions).

Best wishes

[Hifive]

Hi all


Need help with this question:

This year, there are 2300 pupils in Sentosa Primary School. Comparing to last year, there is a 25% increase in the number of boys and a 25% in the number of girls. The total no. of students this year has increased by 15%.
(a) Find the total no. of students in Sentosa Primary School last year.
(b) Find the no. of boys in the school this year.

Managed to solve part (a) with an answer of 2000. Need help on part (b).
Thanks in advance.

[tianzhu]

Hifive:

Hi all


Need help with this question:

This year, there are 2300 pupils in Sentosa Primary School. Comparing to last year, there is a 25% increase in the number of boys and a 25% in the number of girls. The total no. of students this year has increased by 15%.
(a) Find the total no. of students in Sentosa Primary School last year.
(b) Find the no. of boys in the school this year.

Managed to solve part (a) with an answer of 2000. Need help on part (b).
Thanks in advance.

Hi Hifive

I think some information is missing in your question (see highlighted).

The second portion touches on “simultaneous concept”.

Students who are familiar with SE may use it, otherwise, one may use “Units and Parts” or letters of the alphabet to show boys and girls. One may also solve it pictorially.

You may refer to some of the earlier posts for some examples.

A draft solution for your question, I’ll use letters of the alphabet as a representation.

Suppose, there is a 25% decrease in the number of girls .

This year
5B + 3G ------ 2300

Last year
4B + 4G ------ 2000

So, 1B + 1G ------500 and 3B + 3G ------1500

Hence, 2B ------ 2300 – 1500
Therefore 1B ------400

Number of boys this year ------5B ------5*400 ----- 2000

Best wishes

[Hifive]

Hi tianzhu


Many thanks for your quick response.

Yes, the word decrease is missing, so sorry.
Thanks for your explanation and help!

[Brenda10]

Hifive:

Hi tianzhu


Many thanks for your quick response.

Yes, the word decrease is missing, so sorry.
Thanks for your explanation and help!

Hi Hifive

This question look familar and wonder is from which test paper ?

[Hifive]

Hi Brenda10


This question is from A* Maths Problems - Percentage, last question in the booklet. Though they provide solution but DS1 don’t quite understand as they use the model method. The explanation provided by tianzhu is much simpler to understand.

Jiayou for your DD in her coming PSLE oral!

[Brenda10]

Hifive:

Hi Brenda10


This question is from A* Maths Problems - Percentage, last question in the booklet. Though they provide solution but DS1 don't quite understand as they use the model method. The explanation provided by tianzhu is much simpler to understand.

Jiayou for your DD in her coming PSLE oral!

OIC. Thank you Hifive and all the best to your DS too!!! :celebrate:

[tianzhu]

Hifive:

Hi tianzhu


Many thanks for your quick response.

Yes, the word decrease is missing, so sorry.
Thanks for your explanation and help!

Hi

You're welcome.

Best wishes

[htn]

Hi, please help


A pair of hamsters can produce a pair of baby hamsters every month. The baby hamsters take a month before they can reproduce another pair of baby hamsters.
How many pairs of hamsters (adult and baby) will there be by the end of 6 months??
TIA

[KRR]

Hi all,

I need help with this question.

On Saturday pants in a shop were sold at $30 each.
On Sunday the price of pants was reduced and number of pants sold
increased by 50% while the amount collected increased by 25%.

Find the price of pair of pants sold on Sunday.

Thanks in advance.
KRR