Tutor MathsGuru: Ask me for your burning Maths questions!

[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!

[YLH88]

Hi Mathsguru,


Need to trouble you again with the below 2 questions.

1) Shop X sells a table lamp for $300 which is 25% less than the price which Shop Y sells it for.

a) What is the price of the table lamp in Shop Y ?

b) During a sale, both shops offer an equal percentage discount on the table lamp. Mr Song buys the table lamp in Shop X and pays $85 less than the discounted price in Shop Y. What is the percentage discount ?

For part (a), I got the answer is $400, is it correct ?
For part (b), i lost liao ...

2) The figure attached, not drawn to scale, is make up of two overlapping rectanlges, A and B. The ratio of the area of Rectangle A to that of Rectangle B is 2:5. If 25% of Rectangle A is shaded, what fraction of the figure is unshaded ?
I tried working out and got the answer as 25%/550%, is it correct ?

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


Thank you so much!!

[Dharma]

YLH88:

Hi Mathsguru,


Need to trouble you again with the below 2 questions.

1) Shop X sells a table lamp for $300 which is 25% less than the price which Shop Y sells it for.

a) What is the price of the table lamp in Shop Y ?

b) During a sale, both shops offer an equal percentage discount on the table lamp. Mr Song buys the table lamp in Shop X and pays $85 less than the discounted price in Shop Y. What is the percentage discount ?

For part (a), I got the answer is $400, is it correct ?
For part (b), i lost liao ...

2) The figure attached, not drawn to scale, is make up of two overlapping rectanlges, A and B. The ratio of the area of Rectangle A to that of Rectangle B is 2:5. If 25% of Rectangle A is shaded, what fraction of the figure is unshaded ?
I tried working out and got the answer as 25%/550%, is it correct ?

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


Thank you so much!!

Q1
a)\t75% = $300
100% = $400 (Price of lamp in Shop Y)

b)\t25% = $85 (Difference in price of both lamps before and after discount in terms of percentage is the same because both lamps are discounted by the same percentage)

\t100% = $340 (Discounted price of lamp in Shop Y)
\t% discount = $(400-340)/$400 x 100% = 15%

\tCheck discounted price of Lamp in Shop X = 0.85 X $300 = $255
\t$340 - $255 = $85 (OK)

Q2
Ratio of Rect A: Rect B = 2 : 5 = 4 : 10

Ratio of Rect A (Shaded) : Ratio of Rect A (Unshaded) = 1 : 3

Ratio of A (Unshaded) : Ratio of A & B (Shaded) : Ratio of B (Unshaded) = 3 : 1 : (10-1) = 3:1:9

Fraction of figure that is unshaded = 12/13