Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

YLH88:

Hi Mathsguru,


Need your help with the following questions : :?:

1) At first, there were 230 kg of oranges and durians in a market. After 60% of the oranges and 20 kg of the durians were sold, the remaining oranges and durians were of equal weight. What was the original weight of the durians ?

2) There are 480 people in Group X and 20% of them are children. There were 380 people in Group Y and 70% of them are children. After some people were transferred from Group Y to X, 40% of the people in Group X and 50% of the people in Group Y are children. How many people are transferred from Group Y to Group X ?

3) Mrs Winder had some $50 notes and $10 notes. The number of $50 notes is 45% that of $10 notes. She spent 20% of the $50 notes. As a result, she had 192 more $10 notes than $50 notes.
(a) What was the amount of money spent ?
(b) Express the amount of $10 notes as a fraction of the amount of $50 notes left.


Thank you very help !

Hi YLH88,

Here are my solutions. Hope you find them useful!

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=aV5ThOS

http://www.postimage.org/image.php?v=aV5TmO9

http://www.postimage.org/image.php?v=aV5TfjJ

[small]

Hi Mathsguru,


Thanks for the solutions. :celebrate: :celebrate:

Mistaken 'amount' with 'number' for question 3. :oops: :oops:

[YLH88]

Hi Mathsguru, small, coffeecat,


Thank you very much for the solution!! Really appreciate all your help !!

Mathsguru,

For question 1 on the weight of orange and durian, since the remaining weight of durian is also 40% (same as the weight of orange), can we say the 20 kg sold is 60% of the total weight of the durian ? My DS asked me this question, said how come cannot be 60%. Tried working out using 60% = 20 kg, then find 100% = ? kg, but the weight is wrong.

Coffeecat,

for question 1, how did you come out with 2 times of 40% oranges ? Should it be 40% oranges and 40 % durian ? These are P6 level.
[quote]1)Weight of 60% of oranges + 40% oranges + 40%oranges = 230-20=210.
Weight of 40% oranges = 210 * 40 % / 140% = 60kg
weight of durians = 60 + 20 = 80kg [/quote]

[KSP]

Hi mathsguru, I have a question here hope you can help.


Qn) Mike has 157 Chinese and English story books. He sold 3/4 Chinese books and 2/5 English books. He sold 81 books altogether. How many Chnese books did Mike sell?

[CoffeeCat]

YLH88:

Coffeecat,

for question 1, how did you come out with 2 times of 40% oranges ? Should it be 40% oranges and 40 % durian ? These are P6 level.
[quote]1)Weight of 60% of oranges + 40% oranges + 40%oranges = 230-20=210.
Weight of 40% oranges = 210 * 40 % / 140% = 60kg
weight of durians = 60 + 20 = 80kg

[/quote]I express durian's weight as orange's weight. It isn't right to say 40% durianbecause theres no reference made to \"60% of durians weight sold\".

Anyway, 20kg is not 60% of durians weight because the number / weight of oranges and durians are not equal, you only know 60% of oranges sold and some of durians.

[YLH88]

[quote]I express durian's weight as orange's weight. It isn't right to say 40% durianbecause theres no reference made to \"60% of durians weight sold\".


Anyway, 20kg is not 60% of durians weight because the number / weight of oranges and durians are not equal, you only know 60% of oranges sold and some of durians.[/quote]OIC. Thank you!

[mathsguru]

YLH88:

Mathsguru,


For question 1 on the weight of orange and durian, since the remaining weight of durian is also 40% (same as the weight of orange), can we say the 20 kg sold is 60% of the total weight of the durian ? My DS asked me this question, said how come cannot be 60%. Tried working out using 60% = 20 kg, then find 100% = ? kg, but the weight is wrong.

Hi YLH88,

Like what I mentioned in my solution, it is very important for your child to be clear as to what is the \"base\" he is using. We are actually using the weight of the oranges as the base here. What we have actually done is to convert the remaining durian's weight into an equivalent weight of oranges. Hence it is 40% of oranges' weight, not durian's weight. In fact, from the question, we do not know how many percent of the durian's weight the remaining durians take up.

Hope you and your DS can understand what I'm trying to put across.

Cheers,
MathsGuru

[mathsguru]

KSP:

Hi mathsguru, I have a question here hope you can help.

Mike has 157 Chinese and English story books. He sold 3/4 Chinese books and 2/5 English books. He sold 81 books altogether. How many Chnese books did Mike sell?[/b]

Hi KSP,

Here's my solution. The trick here is to eliminate 1 type of book, then we can find out the answer easily.

Hope it helps!

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=aV7gSgS

[KSP]

Like I always say, you are marvellous. Thanks.

[YLH88]

Hi Mathsguru,


Thank you!