Q&A - PSLE Math

[firebird]

Good evening


Please help me on the following P6 maths:

1) If Ahmad and Ben work together, they can complete a jop in 12 days. If
Ahmad and Ben worked together for 3 days, followed by Ben who
worked alone for the next 5 days, they can finish 5/12 of the job. How
many days will each of them need to complete the job if they were to
work alone?

2) Allyson, Betty and Charlene shared to buy a watch for their father on his
birthday. Allyson paid 1/4 of the total share of Betty and Charlene.
Betty paid 1/5 the total share of Allyson and Charlene. If Charalene
paid $56 more than Betty, how much did the watch cost?

Many thanks
firebird

[CoffeeCat]

firebird:

Good evening


Please help me on the following P6 maths:

1) If Ahmad and Ben work together, they can complete a jop in 12 days. If
Ahmad and Ben worked together for 3 days, followed by Ben who
worked alone for the next 5 days, they can finish 5/12 of the job. How
many days will each of them need to complete the job if they were to
work alone?

2) Allyson, Betty and Charlene shared to buy a watch for their father on his
birthday. Allyson paid 1/4 of the total share of Betty and Charlene.
Betty paid 1/5 the total share of Allyson and Charlene. If Charalene
paid $56 more than Betty, how much did the watch cost?

Many thanks
firebird

a)Such typical rate question require step-by-step analysis.

Ahmad + Ben
12 days --> 1 job
1 day --> 1/12 of job
3 days --> 3/12 of job

Ben
5 days --> (5-3)/12 of job = 2/12 of job
1 day --> 2/(12*5) = 2/60 of job
5*6 = 30 days --> 12/12 of job

Ahmad
1 day --> 1/12 - 2/60 = 3/60 of job
20 days --> 60/60 of job.


b)


*********______ __________________
**Charlene|_____|_56_______________|
**********______
*****Betty|_____|

********** ______________
****Allyson|___4units-56___|

We start with the model drawing for Charlene and Betty. We let Betty's share be 1 unit. Charlene's share is 1 unit + 56. Since betty paid 1/5 of the total share of Allyson and Charlene, Allyson and Charlene paid 5 units.
Therefore Allyson's share is 4 units-56
now we use the first sentence, 4 units-56 = 1/4 (2 units + 56)
16 units - 224 = 2 units + 56
14 units = 280
1 unit = 20
Cost of watch = 20 * 6 = 120

[firebird]

Dear Coffeechat


Many thanks
firebird

[kiasiparent]

Awesome question. Keep up the good work.

[Jusmum]

:?: Could you help with this P6 holiday question...


It takes 5 hours for June to complete spring cleaning her house. If Sam helps her, they will take 3 hours to complete. Is Sam were to do alone, how long will she take?

Thanks!

[CoffeeCat]

Jusmum:

:?: Could you help with this P6 holiday question...


It takes 5 hours for June to complete spring cleaning her house. If Sam helps her, they will take 3 hours to complete. Is Sam were to do alone, how long will she take?

Thanks!

Since its a rate question one should start by finding the rate
June
5 hrs --> clean the house completely
1hr --> clean 1/5 of hourse

Sam + June
3 hrs --> clean house completely
1hr --> clean 1/3 house

therefore
Sam
1hr --> clean (1/3 - 1/5) = 2/15 of house
time taken = 15/2 = 7.5 hrs

[Dharma]

Jusmum:

:?: Could you help with this P6 holiday question...


It takes 5 hours for June to complete spring cleaning her house. If Sam helps her, they will take 3 hours to complete. Is Sam were to do alone, how long will she take?

Thanks!

June takes 5 hrs to clean 1 house
June takes 1 hr to clean 1/5 house

June & Sam take 3 hrs to clean 1 house
June & Sam take 1 hr to clean 1/3 house

In 1 hr, Sam can clean (1/3-1/5 = 2/15) of the house.
Sam takes 7.5 hrs to clean the house on her own.

[Jusmum]

Oh, my…thanks so much Coffeecat and Dharma…that was fast…glad I can help my girl now…


But the school has not taught this topic yet…thot it was average question…silly me…

thanks again!

[CoffeeCat]

Jusmum:

Oh, my...thanks so much Coffeecat and Dharma.....that was fast...glad I can help my girl now...


But the school has not taught this topic yet...thot it was average question...silly me...

thanks again!

Hmm i thought rate was out of the syllabus anyway?

[P5G]

Please help.


Paper 2 Q18
http://www.orlesson.org/orp/09Ma/2009-Math-CA1-NanHua.pdf

Please advise how I could find the sum of the numbers in the 10th row without having to list out all the numbers in the 7th, 8th and 9th rows?

TIA.