Tutor MathsGuru: Ask me for your burning Maths questions!

[suiyuan]

mathsguru:

:

:idea: Post your questions here and see how MathsGuru solve them to the best of her ability. Detailed solutions will be posted back in this thread.

So start asking and watch this space!!

Cheers :celebrate: ,
MathsGuru

P/S (Disclaimer, in case you're wondering...):
Although MathsGuru is a full-time Maths tutor, this thread is meant to be an absolutely free resource for parents (or even children) with no strings attached. Just someone who's passionate about Maths and wanna spread the fun in learning Maths with others.

Hi
Thank you for your offer.

1)During a warehouse book sale, Sally spent 62.5% of her money on 24 books and 18 pens. She also spent 25% of her remaining money on 18 files. Each pen costs 8/9 as much as the price of one book. The file costs $7.80 less than a book. Find the total cost of one book and one pen.

2)Mr Lim spent $1496 on some comics and dictionaries altogether. The number of comics bought to the number of dictionaries bought was in the ratio of 3 : 2. A dictionary cost $4 more than a comic. The total cost of the comics was 20% more than the total cost of the dictionaries. Find the cost of a dictionary.

[atutor2001]

suiyuan:

Hi
Thank you for your offer.

1)During a warehouse book sale, Sally spent 62.5% of her money on 24 books and 18 pens. She also spent 25% of her remaining money on 18 files. Each pen costs 8/9 as much as the price of one book. The file costs $7.80 less than a book. Find the total cost of one book and one pen.

2)Mr Lim spent $1496 on some comics and dictionaries altogether. The number of comics bought to the number of dictionaries bought was in the ratio of 3 : 2. A dictionary cost $4 more than a comic. The total cost of the comics was 20% more than the total cost of the dictionaries. Find the cost of a dictionary.

Hi suiyuan

You are very \"naughty\". But the 2nd question is a bit easssy!

Regards

[mathsguru]

suiyuan:

1)During a warehouse book sale, Sally spent 62.5% of her money on 24 books and 18 pens. She also spent 25% of her remaining money on 18 files. Each pen costs 8/9 as much as the price of one book. The file costs $7.80 less than a book. Find the total cost of one book and one pen.

Hi Suiyuan,

Please see my solution and explanation in the attached picture.

http://www.postimage.org/image.php?v=aV1esa5S

Cheers,
MathsGuru

[mathsguru]

suiyuan:

2)Mr Lim spent $1496 on some comics and dictionaries altogether. The number of comics bought to the number of dictionaries bought was in the ratio of 3 : 2. A dictionary cost $4 more than a comic. The total cost of the comics was 20% more than the total cost of the dictionaries. Find the cost of a dictionary.

Sign, have been trying to attach the picture for the past 20 min. I will try again later.

Basically, we need to find out the total cost of comics and total cost of dictionaries first. Then comparing the total cost to the cost of 3 comics and 2 dictionaries (ratio given), we will realise that the number of items bought are 17 times the original ratio (i.e. new ratio is 51:34). After working out, the cost of a dictionary is $20.

Detailed diagrams and working in my picture which I can't seem to attach now (page can't load for postimage.org). :frustrated:

Regards,
MathsGuru

[atutor2001]

mathsguru:

Sign, have been trying to attach the picture for the past 20 min. I will try again later.

Basically, we need to find out the total cost of comics and total cost of dictionaries first. Then comparing the total cost to the cost of 3 comics and 2 dictionaries (ratio given), we will realise that the number of items bought are 17 times the original ratio (i.e. new ratio is 51:34). After working out, the cost of a dictionary is $20.

Detailed diagrams and working in my picture which I can't seem to attach now (page can't load for postimage.org). :frustrated:

Regards,
MathsGuru

I remembered I used to teach my kid the following method :

1. Find the total cost of comic and total cost of dictionary
2. Divide total cost of comic by 3 and Divide total cost of dictionary by 2 (this gives the total cost of the SAME numbers - 1unit, of comic and dictionaries)
3. Find the difference of the answers in step 2 (this gives the difference in total cost of same number - 1 unit, of comic and dictionaries)
4. Divide this difference by 4 (this gives the number of comic or dictionary in 1 unit)
5. Time answer from step 4 by 2 (this gives the actual number of dictionary)
6. Divide the total cost of dictionary by answer from step 5.

Regards.

[tamarind]

Thanks in advance. My friend sent me this question :


I am a three digit number. The digit in the tens place is 6 less than the digit in the hundreds place. The tens place is 2 more than the digit in the ones place. If the digit in the ones place is 5, then I am the number ______.

[KSP]

tamarind:

Thanks in advance. My friend sent me this question :


I am a three digit number. The digit in the tens place is 6 less than the digit in the hundreds place. The tens place is 2 more than the digit in the ones place. If the digit in the ones place is 5, then I am the number ______.

Is this a P1 question?

[mathsguru]

suiyuan:

2)Mr Lim spent $1496 on some comics and dictionaries altogether. The number of comics bought to the number of dictionaries bought was in the ratio of 3 : 2. A dictionary cost $4 more than a comic. The total cost of the comics was 20% more than the total cost of the dictionaries. Find the cost of a dictionary.

Hi Suiyuan,

As promised, here's my detailed diagrams and working. Hope it's self-explanatory enough.

Regards,
MathsGuru

http://www.postimage.org/image.php?v=Pq1zUxsr

[KSP]

mathsguru:

suiyuan:

2)Mr Lim spent $1496 on some comics and dictionaries altogether. The number of comics bought to the number of dictionaries bought was in the ratio of 3 : 2. A dictionary cost $4 more than a comic. The total cost of the comics was 20% more than the total cost of the dictionaries. Find the cost of a dictionary.

Hi Suiyuan,

As promised, here's my detailed diagrams and working. Hope it's self-explanatory enough.

Regards,
MathsGuru

Hi mathsguru,

How much time is allocated for such question like this in real exam?

[acforfamily]

tamarind:

Thanks in advance. My friend sent me this question :


I am a three digit number. The digit in the tens place is 6 less than the digit in the hundreds place. The tens place is 2 more than the digit in the ones place. If the digit in the ones place is 5, then I am the number ______.

If the digit in the ones place is 5,
and The tens place is 2 more than the digit in the ones place.
then the tens place is 7

The digit in the tens place is 6 less than the digit in the hundreds place
then the digit in the hundred place is 7+6 = 13 ??
Is there something wrong here?