Tutor MathsGuru: Ask me for your burning Maths questions!

[tianzhu]

Emelyn:

Mr Tay bought a massage chair for $888. He sold it to Mr Yeo for $850. He later bought the massage chair back from Mr Yeo for $900 and sold it to Mrs Tan for $1000. How much did Mr Tayy gain ?

Hi
The cost incurred by Mr Tay ---- (888 + 900) -----1788
He received (850+1000) ---- 1850
Therefore, he gained (1850 – 1788) ---- 62

Best wishes

[YLH88]

Hi CoffeeCat, Dharma,


Thank you so much!!

Regards

[P5G]

Dharma:

P5G:

[quote=\"Emelyn\"]I have one question :


Mr Tay bought a massage chair for $888. He sold it to Mr Yeo for $850. He later bought the massage chair back from Mr Yeo for $900 and sold it to Mrs Tan for $1000. How much did Mr Tayy gain ?

MTIA !

888 - 850 = 38 - loss

900 - 850 = 50 -- loss

1000 - 900 = 100 -- gain

100 - 38 - 50 = $12 gain

Hi P5G

888 - 850 = 38 - loss

900 - 850 = 50 -- loss (This line double counts the sales of 850 & purchase of 900)

1000 - 900 = 100 -- gain

100 - 38 - 50 = $12 gain (Need to remove the 50)

Should be

100 – 38 = 62 (Gain)[/quote]
Thanks Mr Dharma.


888 - 850 = 38 - loss

900 - 850 = 50 -- loss How could I have counted the loss when the chair was not sold yet?

1000 - 900 = 100 -- gain

100 - 38 - 50 = $12 gain


What a silly mistake that I made for counting the loss before the chair was sold!

100 - 38 = $62 gain

[CoffeeCat]

Emelyn:

CoffeeCat:

[quote=\"Emelyn\"]I have one question :


Mr Tay bought a massage chair for $888. He sold it to Mr Yeo for $850. He later bought the massage chair back from Mr Yeo for $900 and sold it to Mrs Tan for $1000. How much did Mr Tayy gain ?


MTIA !

do it step-by-step...
Or
when he buy, money is being gone from his pocket (so we will minus) and when he sell, money is being earned (so we will add).

-$888 + $850 -$900 + $1000
(if you are uncomfortable with a negative integer at the front then use the \"working backwards\" )

$1000 - $900 + $850 - $888 = $62

The qn is actually from a colleague.
Her DD1 (P3) and DD2 (P2) teachers both said answer is $12.
I wonder why.....[/quote]If we are right and the teachers wrong then this is most disturbing.
p5g you might have pointed out how the teachers got their answer...

[mathsguru]

rain29:

Hi Mathsguru,


Need your help for the following P4 maths questions.

1) The sum of Ben's age and his younger brother's age is 26. The product of their ages is 144. What is Ben's age in 20 years' time?

2)At a cupcake baking competion, Alan baked 55 fewer cupcakes than Tom while Sally baked twice as many cupcakes as what Alan and Tom baked together. If 3 of them baked a total of 1125 cupcakes, how many cupcakes did Tom bake?

Thanks

Hi Rain29,

Here are my solutions. Hope they help!

Cheers,
MathsGuru

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

http://www.postimage.org/image.php?v=TskEMY0

[mathsguru]

Millicent:

Dear Mathsguru,


Need your help to solve this question. With appreciation and many thanks.

Four boxes A,B,C and D contained a total of 265 pens at first. Then the number of pens in A was increased by 15; the number in B was decreased by 10; the number in C was doubled; and the number in D was halved. As a result, the number of pens in each box was the same. Find the number of pens in each box at first.

Hi Millicent,

Here's my solution.

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=TskF0VS

[mathsguru]

OngMum:

Hi Mathsguru, we need your guidance on the below questions.


Qn 1, Shop A has 156kg of rice while Shop B has 72kg of rice. Each shop sold an equal amount of rice and after that the ratio of the amount of rice left in their shop was 4:1. Find out how much rice has been sold.

Qn 2, 6/14 of the chairs in the hall are in rows of 13. Half of the chairs in the hall are in rows of 7. There are 112 more chairs in rows of 7. The rest of the chairs are stacked up. Find out the total number of chairs in the hall.

Many thanks.

Cheers!

Hi OngMum,

Here're my solutions. Hope they help!


MathsGuru

http://www.postimage.org/image.php?v=Pq8yQ00

http://www.postimage.org/image.php?v=gxmvya0

[mathsguru]

firebird:

Dear Mathsguru


I am totally lost on the following P6 maths, especially question 1, which look easy, but i could not do, please help:

1) Victor wants to travel from Town X to Town Y. If he drives at an average speed of 60km/h, he would reach Town Y at 10.30am. If he drives at an average speed of 80km/h, he would reach Town Y at 9.30am.
(a) Find the distance between Town X and Town Y .
(b) At what average speed should he drive if he wants to reach Town Y at 9.30 am?

2) A piggy bank contained some fifty-cents coins and twenty-cents coins in the ratio of 5:2. When 36 fifty-cents coins were taken out and replaced by the same number of twenty-cents coins, the ratio of the number of fifty-cents coins to twenty-cents coins became 1:4.
a) What was the value of the twenty-cents coins at first?
b) How much money was in the piggy bank at first?

Hi Firebird,

Please take a look at my solutions. I've explained abit on the speed question. You can try to make use of the \"speed vs. time ratio\" in future for speed questions which gives very little info on distance, time, etc. But for part (b) of the question, is there a typo? Cos the question seems to be asking what is stated in the question already.

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=Pq8CSqA

http://www.postimage.org/image.php?v=Pq8E8f9

[mathsguru]

Vanilla Cake:

Dear Mathsguru,

Pls help to provide solution for this RGPS P6 SA1 2009 P2 Q18:

Container A contains 250 red marbles and 200 blue marbles. Container B contains 600 red marbles and 150 blue marbles. How many red and blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in Container B are red? (5 marks)

Thanks

Hi Vanilla Cake,

Here's my solution. Hope you can understand the model drawings...

Cheers,
MathsGuru

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

[mathsguru]

underthesea:

Can someone help me with this maths question:


There are 2 boxes. Box and Box Y, both of which contain pens and erasers only. The respective numbers of pens and erasers in Box X are in the ratio 1:3. The respective numbers of pens and erasers in Box Y are in the ratio 5:6. The number of items in Box X is thrice the number of items in Box Y.
(a) Find the ratio of the number of pens in Box Y to the number of pens in Box X.
(b) Knowing that there are 100 more erasers in Box Y than in Box X, find the number of erasers in Box Y.

anything wrong with the question?

TIA

Hi Underthesea,

I can only solve part (a). I think there's something wrong with the question as Box Y should not have more erasers than Box X if my answer in (a) is correct.

Perhaps you can re-check with the source of the question?


MathsGuru

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