Tutor MathsGuru: Ask me for your burning Maths questions!

[Maths Monster]

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[david59]

david59:

chrisho:

2 simple questions that need to find better way to explain to my son. d


1. James had twice as many marbles as Bob. After James lost 240 marbles, Bob had 3 times as many marbles as James. How many more marbles did James have Than Bob at first.

2.Peter is 8 years old and his mother is 30 years older than he. how old will Peter be when his mother is thrice his age?

TQ

Hi, This is the model method to solve this kind of question. I have to hurry off so the drawing may not be so nice. God bless.
http://www.postimage.org/image.php?v=gxBEfFi

Using Model method for qn 2.


http://www.postimage.org/image.php?v=PqbJTV0

[Dharma]

abc_parent:

Guru,


The question is like this:
A mechanical pencil cost $8. A pen cost 25% more. Jason paid $210 for some mechanical pencils and pens. 80% of what he bought were mechanical pencils. How many more mechanical pencils than pens did he buy?

Answer: 15

I keep getting 30. Is my answer wrong or given answer wrong? Please show me step by step again? Thanks.

Cost of mech pencil : $8 x 8u = $64u
Cost of pens : $10 x 2u = $20u
Total cost = $84u

$84u = $210
1u = 2.5

Difference in qty = (8u - 2u) = 6u = 6 x 2.5 = 15

[Maths Monster]

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[Maths Monster]

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[Dharma]

Herbie:

Please assist with the following qns


Q1. Lynn had 2250 beads. She transferred 1/6 of the no. of beads from Box A to Box B. Then she transferred 3/8 of the new no. of beads from Box B to Box A. Later, she transferred 2/9 of the new number of beads from Box A to Box B. In the end, the ratio of the no. of beads in Box A to Box B was 28:17. How many beads were there in Box B at first?


Please solve using unit method if possible.

Thanks!

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

[Vanilla Cake]

Herbie:

Q2. Jane takes 10 days to complete stringing a no. of beads. Sharon takes 18 days to complete the same job. Jane started strining the beads first and left the remainder to Sharon to complete. They took 14 days to complete the job together. How many days did Jane spend on the job?

Hi Herbie,

For your reference, your Q2 was first posted by Tianzhu on http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=310.
kiasiparent posted his solution on 22 Apr 2009 22:11 and Dharmaratnam posted his solution on 23 Apr 2009 06:31.

kiasiparent's solution
In 1 day, Jane can complete 1/10 of the strings whereas sharon can complete 1/18 of the string.

I believe the fastest way to do this question is to do guess and check.

Since they took 14 days together, try jane 1 day and sharon 13 days etc.
try jane 2 days and sharon 12 days.

Then you will realise that jane 5 days and sharon 9 days will be the correct answer as 5/10 + 9/18 = 1 whole string.

You can also do simultaneous equation.
Assume the whole string is 180 parts long.

Then Jane can do 18 parts in 1 day and sharon can do 10 parts in 1 day.
Let the no of Janes day be J and the no of Sharon days be S.
Doing simultaneous equation:
J + S = 14
18J + 10S = 180

Therefore, S = 14 - J
18J+ 10(14 - J)= 180
8J = 40
J = 5 days.

Dharmaratnam 's solution
Jane can complete 1/10 of the strings in 1 day
Sharon can complete 1/18 of the strings in 1 day

If Jan takes N days, Sharon will take (14-N)days to complete the work.

Therefore,

N/10 + (14-N)/18 = 1

N= 5

Jane took 5 days

Submitted by VC's mum.

[lemofish]

Vanilla Cake:

Herbie:

Q2. Jane takes 10 days to complete stringing a no. of beads. Sharon takes 18 days to complete the same job. Jane started strining the beads first and left the remainder to Sharon to complete. They took 14 days to complete the job together. How many days did Jane spend on the job?

Hi Herbie,

For your reference, your Q2 was first posted by Tianzhu on http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=310.
kiasiparent posted his solution on 22 Apr 2009 22:11 and Dharmaratnam posted his solution on 23 Apr 2009 06:31.

kiasiparent's solution
In 1 day, Jane can complete 1/10 of the strings whereas sharon can complete 1/18 of the string.

I believe the fastest way to do this question is to do guess and check.

Since they took 14 days together, try jane 1 day and sharon 13 days etc.
try jane 2 days and sharon 12 days.

Then you will realise that jane 5 days and sharon 9 days will be the correct answer as 5/10 + 9/18 = 1 whole string.

You can also do simultaneous equation.
Assume the whole string is 180 parts long.

Then Jane can do 18 parts in 1 day and sharon can do 10 parts in 1 day.
Let the no of Janes day be J and the no of Sharon days be S.
Doing simultaneous equation:
J + S = 14
18J + 10S = 180

Therefore, S = 14 - J
18J+ 10(14 - J)= 180
8J = 40
J = 5 days.

Dharmaratnam 's solution
Jane can complete 1/10 of the strings in 1 day
Sharon can complete 1/18 of the strings in 1 day

If Jan takes N days, Sharon will take (14-N)days to complete the work.

Therefore,

N/10 + (14-N)/18 = 1

N= 5

Jane took 5 days

Submitted by VC's mum.

I used ratio to solve this problem.

Ratio of Jane's speed to Sharon's speed = 10:18 = 5:9
Since they complete the job in 14 days, therefore Jane spent 5/14*14 = 5 days on the job.

[Herbie]

Thanks! VC, Maths Monster, Dharma and Lemofish for providing the solutions.


Can help to solve the qn below:
A group of people met at a party. Each person shook hands with everyone. Mr Li shook hands 3 times as many men as women. Mrs Lim shook hands with 4 times as many men and women.

How many men and women are there?

I dun understand the model solution provided by Mr tianzhu.

Can someone explain the solution again???

Many thanks!

[Dharma]

Herbie:

Thanks! VC, Maths Monster, Dharma and Lemofish for providing the solutions.


Can help to solve the qn below:
A group of people met at a party. Each person shook hands with everyone. Mr Li shook hands 3 times as many men as women. Mrs Lim shook hands with 4 times as many men and women.

How many men and women are there?

I dun understand the model solution provided by Mr tianzhu.

Can someone explain the solution again????

Many thanks!

Mr Li : 1
Men : 3u
Women : 1u

Mrs Lim : 1
Men : 4p
Women : 1p

Total no. of women = 1u = 1p + 1
Total no. of men = 3u + 1 = 4p

3p + 3 + 1 = 4p
1p = 4
1u = 4 + 1 = 5
Total no. of men = 4p =4( 4) = 16
Total no. of women = 1u = 5