Q&A - PSLE Math

[Dharma]

Belle2011:

Dear everybody,

Happy New Year to you.

Here is another question from a worksheet given by a teacher from Just Education.

Karen is about as many days as her mother is in weeks and Karen is as months as her grandpa is in years. Karen, her mother and her grandpa are 160 years old altogether. How old is her grandpa?
(model answer: 96)

My problem is I dont really understand some parts in this question and thus unable to solve.

Thanks.

Cheers,
Belle.

Karen : Mother = a days : a weeks = a/7 weeks : a weeks = 1 : 7
Karen : Grandpa = b months : b years = b/12 years : b years = 1 : 12

Karen : Mother : Grandpa : 1 : 7 : 12
1u + 7u + 12u = 160
20u = 160
1u = 8

Grandpa's age = 12u = 12 x 8 = 96 years old

[Belle2011]

Dharma:

Belle2011:

Dear everybody,

Happy New Year to you.

Here is another question from a worksheet given by a teacher from Just Education.

Karen is about as many days as her mother is in weeks and Karen is as months as her grandpa is in years. Karen, her mother and her grandpa are 160 years old altogether. How old is her grandpa?
(model answer: 96)

My problem is I dont really understand some parts in this question and thus unable to solve.

Thanks.

Cheers,
Belle.

Karen : Mother = a days : a weeks = a/7 weeks : a weeks = 1 : 7
Karen : Grandpa = b months : b years = b/12 years : b years = 1 : 12

Karen : Mother : Grandpa : 1 : 7 : 12
1u + 7u + 12u = 160
20u = 160
1u = 8

Grandpa's age = 12u = 12 x 8 = 96 years old

Dear Dharma,
Thanks very much for your prompt reply.

May I ask:
why consider weeks for Karen: Mother?
why consider years for Karen: Grandpa?
Also,
when you combine the 3 persons ie Karen: Mother: Grandpa, can we simply lump the ratios since Karen: Mother is originally in weeks and Karen: Grandpa is originally in years, if you know what I mean?
Thanking you in advance.

Cheers,
Belle.

[Hifive]

Dharma:

The final condition is :

The 3 girls had the same amount of money( I assumed 6u for each of the 3 girls).
Notice that Queenie's money did not change at all. So, Queenie had 6u at the beginning too.
Since the qn tells us that ratio of money Peter to Queenie at first is 1:2.
Therefore, Peter must have had 3u at first.

Hi Dharma

Thanks. I can understand now.

[tianzhu]

Belle2011:

May I ask:
why consider weeks for Karen: Mother?
why consider years for Karen: Grandpa?

Hi Belle2011

Good Morning

Another way to look at it to use the number of days as the basis of comparison.

The ratio of Karen’s age to her mother is 1:7 (7 days in a week)

The ratio of Karen’s age to her grandpa is 1:12 (12 months in a year)

Ratios is a comparison of two or more quantities of the same kind, so we convert the months and weeks into number of days.

Therefore, the ratio of Karen’s age to her grandpa is 28:336 (we assume that 1 week --- 7 days, 1 month --- 4 weeks)
Use equivalent ratios to reduce to the lowest term, we have 1:12

So the ratios (in the form of days)
Karen:mother --- 1:7
Karen:grandpa --- 1:12

Karen:mother:grandpa --- 1:7:12

1u+7u+12u --- 160 (Total age is 160)

20u --- 160
1u --- 8

12u ---8*12 --- 96 (grandpa’s age)

Best wishes

[Belle2011]

Dear tianzhu,

Once again, thanks very much for your solution.

Cheers,
Belle.

[CTong]

zara had 70 more dresses than skirts, she sold 3/4 of the dresses and 3/5 of the skirts. What fraction of the remaining clothes that Zara had were skirts?

[tianzhu]

CTong:

zara had 70 more dresses than skirts, she sold 3/4 of the dresses and 3/5 of the skirts. What fraction of the remaining clothes that Zara had were skirts?

Hi CTong

Please check your question again, looks like there is missing information.

Best wishes

[Brenda10]

tianzhu:

CTong:

zara had 70 more dresses than skirts, she sold 3/4 of the dresses and 3/5 of the skirts. What fraction of the remaining clothes that Zara had were skirts?

Hi CTong

Please check your question again, looks like there is missing information.

Best wishes

Hi Tiaznhu

This question should be from P5 SCGS SA2 2009 Qn18.

Zara has 70 more dresses than skirts. She sold 3/4 of the dresses and 3/5 of the skirts. She sold 126 more dresses than skirts. What fraction of the remaining clothes that Zara had were skirts ?

Thank you

[CTong]

Sorry, my son wrote the question for me.


Any answer for it?

[tianzhu]

Brenda10:

This question should be from P5 SCGS SA2 2009 Qn18.

Zara has 70 more dresses than skirts. She sold 3/4 of the dresses and 3/5 of the skirts. She sold 126 more dresses than skirts. What fraction of the remaining clothes that Zara had were skirts ?

Hi CTong/Brenda10

A quick one, you may avoid working with decimals by working this way.
It's helpful to draw a simple MD.

Consider skirts sold first.
Skirts sold --- 3 units

Next, consider dresses sold
Dresses sold --- 3 units + 126

Hence , one quarter of dresses ----- 1 unit+42
Hence, total number of dresses ----- 4units+168

Total number of skirts ----- 5 units

4 units + 168 ----- 5 units+70
1 unit -----98

Skirts remaining ------2*98 ------196
Dresses remaining ------- 140
Clothes remaining ------336

Skirts remaining/remaining clothes -----196/336 ------ 7/12

Best wishes