Tutor MathsGuru: Ask me for your burning Maths questions!

[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 stringing 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,

Your question is similar to this question posted in another forum before except that the names are changed in your question.

Jenny takes 10 days to complete a dress. Sally takes 18 days to complete the same job. Jenny started making the dress first and left the remainder for Sally to complete. They took 14 days to complete the job together. How many days did Jenny spend on the job?

Using supposition to solve:
Based on per unit time:

Jane : 1 day -> 1/10 of the job-> 9/90 of the job
Sharon: 1 day ->1/18 of the job-> 5/90 of the job

Difference = (9-5)units = 4 units
Total = 90 units

Let's say Jane did all the work, 14x9 = 126 units
Excess = (126-90) units = 36 units
means that Jane would have overdone by 36 units if she did all the work

We know that the difference is 4 units, so 36 divided by 4 = 9 days.
9 days would be taken by Sharon if both worked together and Jane would spend 5 days on the job.
Number of days that Jane spent on the job was 5.

You can try assuming Sharon did all the job instead and should get the same answer.

The alternative method is guess and check.

[Vanilla Cake]

Herbie:

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?

After

A : B
28 : 17

45u = 2250
u = 50

A=1400
B=850

7/9(A)=1400
2/9(A)=400

A=1800
B=450

5/8(B)=450
3/8(B)=270

A=1530
B=720

5/6(A)=1530
1/6(A)=306

A=1836
B=414

There were 414 beads in Box B at first.

Your 2 questions sound familiar, could you pls advise the source?
Thanks.

PS : Your Q1 has been discussed before in KSP forum.I think it was posted by Uncle Tianzhu.

[Vanilla Cake]

Herbie:

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?

Source : http://www.wendykoh.com/08/primary6-rgssa1-maths.pdf - 5 marks.

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?

Source : http://www.wendykoh.com/08/primary6-rgssa1-maths.pdf - 3 marks.

This question - Jane & Sharon was posted http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280 and different methods were provided to solve.You may wish to take a look at them.Thanks.

[abc_parent]

Thank you Maths Monster and 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.

[Vanilla Cake]

abc_parent:

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?

Hi abc_parent,

Pls see my solution while waiting for Mathsguru/Maths Monster/Dharma and others to come forward and provide their solutions. Hope this helps you.

Cost of a Mechanical pencil = $8
Cost of a pen = 1.25x$8 = $10
Ratio of mechanical pencils to pen = 80: 20 = 4:1 (numbers)

Cost of 1 set of mechanical pencil & pen = 4x$8 + 1x$10 = $42
Jason paid $210 which was $210/$42 = 5 sets.

Difference between mechanical pencil and pen in a set = 4-1 = 3
3x5 = 15.

Jason bought 15 more mechanical pencils than pens

[small]

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.

Hi abc_parent,

The answer should be 15.

This is my solution, hope that mathsguru can give you more detail solution.

http://www.postimage.org/image.php?v=Tsz6kDA

[Maths Monster]

delete

[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