Tutor MathsGuru: Ask me for your burning Maths questions!

[kancheongmum]

x6michelle9x:

kancheongmum:

[quote=\"x6michelle9x\"]Hi, I would appreciate if someone can help to solve this problem without using algebra, thanks in advance!


The average cost of a few books was $8. After a book which costs $32 was added, the average cost becomes $12. How many books are there now?

Hi, thanks for the prompt reply
However, I can't figure out the rationale behind '$32 - $12 = $20'. Why does $32-$12 equals to 'minus out the book that was added'. Could you help me with this? Thanks a lot!

[/quote]Hi

Maybe is clearer for me to say this way:

$32 - $12 =$20

$20 is the total difference in amount over the same number of books(before one book is added)

\"minus out the book that was added\" I mean the new average amount must be subtracted from the price of the additional book.

I understand the confusion. It took me sometime to explain to my son. I draw diagrams to help him understand but sorry I don't know how to illustrate here.

Hope this helps

[pecalis]

kancheongmum:

x6michelle9x:

Hi, I would appreciate if someone can help to solve this problem without using algebra, thanks in advance!


The average cost of a few books was $8. After a book which costs $32 was added, the average cost becomes $12. How many books are there now?

Hi, thanks for the prompt reply
However, I can't figure out the rationale behind '$32 - $12 = $20'. Why does $32-$12 equals to 'minus out the book that was added'. Could you help me with this? Thanks a lot!

New price - new average = 32 - 12 = 20
The excess 20 is spread out evenly to bring the ave of the rest from 8 to 12 ie. 12 - 8 = 4 (each book increase by 4)
so 20/4=5, therefore, there are 5+1=6 books now
HTHs

[Daddy]

Hi


I have a question to ask. Thanks…

1. The number of boys to the number of girls attending Tuition class A and Tuition class B are 2:1 and 2:7 respectively. The ratio of the total number of pupils in Tuition class A to that of tuition class B is 2:3.
a) What is the ratio of the number of boys in Tuition class A to the number of boys in Tuition class B? Give your answer in simplest form.
b) There are 35 more girls than boys in Tuition class B. For both tuition classes, each cild has to pay $280 every month. How much fess does both tuition classes collect in all for 12 months?

Thanks
Daddy

[Muffins]

hi Daddy, are you sure that you have written the question correctly? Because, If the total number of B + G for Tuition A is 2 + 1 = 3, and for B, 2 + 7 = 9, the ration would be 3 : 9 = 1 : 3, not 2 : 3…


Thanks…

[Mathmaniac]

Daddy:

Hi


I have a question to ask. Thanks..

1. The number of boys to the number of girls attending Tuition class A and Tuition class B are 2:1 and 2:7 respectively. The ratio of the total number of pupils in Tuition class A to that of tuition class B is 2:3.
a) What is the ratio of the number of boys in Tuition class A to the number of boys in Tuition class B? Give your answer in simplest form.
b) There are 35 more girls than boys in Tuition class B. For both tuition classes, each cild has to pay $280 every month. How much fess does both tuition classes collect in all for 12 months?

Thanks
Daddy

a) (2/3 x 2) : (2/9 x 3) = (12/9) : (6/9) = 12:6 = 2:1

b) (7/9 - 2/9) of class B = 35
5/9 of class B = 35
class B = 35 x 9/5 = 63
class A = 63 x 2/3 = 42
total = 63+42 = 105
fees = 105 x $280

[Muffins]

O… I get it… Thanks MathManiac!!!

[Mathmaniac]

Muffins:

O... I get it..... Thanks MathManiac!!!

No problem. You must have misread the question.

[kittybank]

Dear all,


Please help me with this:
3/5 of Alethea’s bangles was twice as many as Millicent’s bangles. Millicent and Amber had bangles in the ration of 6:7. All of them paid a combined total of $528 on the bangles. Given that each bangle cost the same, how much did Alethea pay for her bangles?

Answer is $320. Do you think the question has omitted the word "cost" somewhere in the question?

Thank you.

[Mathmaniac]

wormy:

Dear all,


Please help me with this:
3/5 of Alethea's bangles was twice as many as Millicent's bangles. Millicent and Amber had bangles in the ration of 6:7. All of them paid a combined total of $528 on the bangles. Given that each bangle cost the same, how much did Alethea pay for her bangles?

Answer is $320. Do you think the question has omitted the word \"cost\" somewhere in the question?

Thank you.

There is a problem with the question.

[kittybank]

Mathmaniac:

wormy:

Dear all,


Please help me with this:
3/5 of Alethea's bangles was twice as many as Millicent's bangles. Millicent and Amber had bangles in the ration of 6:7. All of them paid a combined total of $528 on the bangles. Given that each bangle cost the same, how much did Alethea pay for her bangles?

Answer is $320. Do you think the question has omitted the word \"cost\" somewhere in the question?

Thank you.

There is a problem with the question.

It's taken from CHIJ 2008 SA1 paper. Any one out there knows where is the typo?