KiasuParents - Parenting in Singapore

Hi

Can someone help on this question? (Without using calculator, show the workings)

Is there a Math expert who can explain why the solution of the question:
In 2006, the price of one litre of petrol was $2.30. If the price of petrol in 2006 was 15% less than the price in 2005, calculate the price of one litre of petrol in 2005:
Is as follows:
Price of 1 litre of petrol in 2005 = 100/85 X 2.3 = $2.71

My question is: why is it 100/85 ( as in 100 divided by 85)?

Thanks so much!!! Really appreciate clarification on this

blissful mummy wrote:Is there a Math expert who can explain why the solution of the question:
In 2006, the price of one litre of petrol was $2.30. If the price of petrol in 2006 was 15% less than the price in 2005, calculate the price of one litre of petrol in 2005:
Is as follows:
Price of 1 litre of petrol in 2005 = 100/85 X 2.3 = $2.71

My question is: why is it 100/85 ( as in 100 divided by 85)?

Thanks so much!!! Really appreciate clarification on this

For questions on percentage, one has to be very clear of which quantity is equivalent to 100%, usually it is the original quantity or the quantity that we are comparing with will be 100%.
In this question,we are comparing the price of one litre of petrol in 2006 to the price in 2005. Hence 2005 price is equivalent to 100% and 2006 being 15% lesser, will be 85%.
Thus,2006: 85% - $2.30
2005:100%-$2.30/85x100=$2.71

Hi Piggylalala, really appreciate your clear and concise explanation, I get it now! Thanks v much for your kind help, really appreciate your time Have a lovely week ahead!

blissful mummy wrote:Hi Piggylalala, really appreciate your clear and concise explanation, I get it now! Thanks v much for your kind help, really appreciate your time Have a lovely week ahead!

Glad that I could help. U have a nice week ahead too.

Sec 1 math has quite a fair bit of algebra , which I prefer.
Ds told me his class mate use psle model method to solve the story sum
Teacher gave that boy Zero ! Recall back, pri kids spends so many yrs
On hateful model , ended up not allowed in sec sch - Wat happen to math syllabus ? Pri n sec no linkages , why make the pri kids " suffer " so much nei

Need help on this question.

The price of a sofa is $x. A man buys the sofa on hire purchase according to the following terms: a downpayment of 25% and the remaining to be paid in monthly installments over 30 months at a simple interest rate of 12% per annum. Given that his monthly instalment is $52, find the value of x.

cftan wrote:Need help on this question.

The price of a sofa is $x. A man buys the sofa on hire purchase according to the following terms: a downpayment of 25% and the remaining to be paid in monthly installments over 30 months at a simple interest rate of 12% per annum. Given that his monthly instalment is $52, find the value of x.

Please let us know if you need further explanation, our team of ex IP school/RGS/NYGH teachers are here to support you.

MyPillow wrote:Sec 1 math has quite a fair bit of algebra , which I prefer.
Ds told me his class mate use psle model method to solve the story sum
Teacher gave that boy Zero ! Recall back, pri kids spends so many yrs
On hateful model , ended up not allowed in sec sch - Wat happen to math syllabus ? Pri n sec no linkages , why make the pri kids " suffer " so much nei

Hi Mypillow,

There is a link between model and algebra actually. To certain extent, model is indeed a simplified pictorial presentation of algebra.

Primary school students cannot understand algebra well as it is quite abstract. So we use model approach to help students in understanding and visualising the questions.
However, model approach has its limitation as it is a simplified substitution of algebra. Therefore, teachers in secondary school insist that the students need to learn the more advanced and proper algebra, rather than always stick to model.

Cheers!

MyPillow wrote:Sec 1 math has quite a fair bit of algebra , which I prefer.
Ds told me his class mate use psle model method to solve the story sum
Teacher gave that boy Zero ! Recall back, pri kids spends so many yrs
On hateful model , ended up not allowed in sec sch - Wat happen to math syllabus ? Pri n sec no linkages , why make the pri kids " suffer " so much nei

This is the very reason why I always encourage students to pick up algebra at Primary 5 if they are competent, or Primary 6, to mitigate the loss of marks due to inability to draw models.


Regards,
Eric
passioninlearning.wordpress.com