Tutor MathsGuru: Ask me for your burning Maths questions!

[Tang]

atutor2001:

acehkr3009:

Hi Parents,


Here is a question fr my son's math assignment, which I think may be incorrect...need your advise..

The average of a set of 4 numbers is M. If 79 is added to this set of number, the average becomes M + 3. What is the value of M?

Thanks.

Hi, if I am not wrong M=64. The working goes like this :

New average (M+3) = 79 - (3x4) = 67
Old average (M) = 67 - 3 = 64

Hi,


Total of 4 numbers --> 4M

Total of 5 numbers --> 5M + 5 x 3 = 5M + 15

So 5th number --> 5M + 15 - 4M = M + 15

M + 15 --> 79
M --> 79 - 15 = 64

[beauty queen]

Please help me with this question,


There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.

[clblinym]

Dharma:

clblinym:

Hi, Parents


Can anyone help solve the following math question. Many thanks.

The answer given is 5:2.

Amy
http://www.postimage.org/image.php?v=aVi95Tr

Ratio of Area of AEB : Area of AEC : Area of ADE = 1 : 4 : 2

Area of ABC = 1/2 X AB x Perpendicular Height
Area of ADC = 1/2 x DC x Perpendicular Height

AB : DC = Area of ABC : Area of ADC = (1+4 ) : 2 = 5 : 2

Dear Dharma,
Thank you so much for your great help.
My son and I fully understand your explanation.
We really appreciate your helpfullness.

I just want to check with you if it is a typo for the sentence.
Ratio of Area of AEB : Area of AEC : Area of ADC = 1 : 4 : 2

[Dharma]

clblinym:

Dharma:

[quote=\"clblinym\"]Hi, Parents


Can anyone help solve the following math question. Many thanks.

The answer given is 5:2.

Amy
http://www.postimage.org/image.php?v=aVi95Tr

Ratio of Area of AEB : Area of AEC : Area of ADE = 1 : 4 : 2

Area of ABC = 1/2 X AB x Perpendicular Height
Area of ADC = 1/2 x DC x Perpendicular Height

AB : DC = Area of ABC : Area of ADC = (1+4 ) : 2 = 5 : 2

Dear Dharma,
Thank you so much for your great help.
My son and I fully understand your explanation.
We really appreciate your helpfullness.

I just want to check with you if it is a typo for the sentence.
Ratio of Area of AEB : Area of AEC : Area of ADC = 1 : 4 : 2[/quote]Sorry for the typo error. Yes , it is ADC

[maths6a]

beauty queen:

Please help me with this question,


There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.

http://www.postimage.org/image.php?v=aVmQl6J
[/img]

[tianzhu]

acehkr3009:

Hi,


Need some help on this question.

Not sure why question appear so small.

Here is the retype of the question:

If W & Y is the mid-point of AB and CD respectively, and Z & X are any points along AD and BC respectively. What is the fraction of the shaded portion ?

Thanks.

http://www.postimage.org/image.php?v=Ts7ucsS

Hi

I cannot read the image clearly, I am wondering if there is any indication of the relationship between Z and X in the question, eg the ratio of point Z to point X.

When I clicked at the image, I got a warning message like Opening this website may put your security at risk

Best wishes

[trytry]

Hi, need help.

This question was given as prelim practice:

Tom was driving from his office back to his house. As he was sick, he drove 20km/h slower. As a result, he reached home 10 minutes later.The distance between his office and house is 40km. What is his usual speed?

Tia.

[acehkr3009]

Hi TianZhu,


On the question sheet, there isn't any relation or ratio for Z & X.

Not sure why you can't see the image, but let me to draw the diagram with words....

ABCD is a rectangle.

AB (left) & CD (right) are the breadth of the rectangle.

W is the midpoint of AB and Y is the midpoint of CD.

Z is anypoint along AD and X is anypoint along BC.

Shaded portion is triangle ZDY.

Hope this is helpful of how the diagram look.

Not sure if this P5 question is flaw.

Thanks.


http://www.postimage.org/image.php?v=PqEgXC9

[Kiasu Friend]

acehkr3009:

Hi TianZhu,


On the question sheet, there isn't any relation or ratio for Z & X.

Not sure why you can't see the image, but let me to draw the diagram with words....

ABCD is a rectangle.

AB (left) & CD (right) are the breadth of the rectangle.

W is the midpoint of AB and Y is the midpoint of CD.

Z is anypoint along AD and X is anypoint along BC.

Shaded portion is triangle ZDY.

Hope this is helpful of how the diagram look.

Not sure if this P5 question is flaw.

I think the question is flawed or incomplete. Unless the relationship between Z and X is stated, I wonder how the area of the shaded region (vs) unshaded can be estimated. Please check with the source of this question.

Thanks.

[acehkr3009]

Tang:

atutor2001:

[quote=\"acehkr3009\"]Hi Parents,


Here is a question fr my son's math assignment, which I think may be incorrect...need your advise..

The average of a set of 4 numbers is M. If 79 is added to this set of number, the average becomes M + 3. What is the value of M?

Thanks.

Hi, if I am not wrong M=64. The working goes like this :

New average (M+3) = 79 - (3x4) = 67
Old average (M) = 67 - 3 = 64

Hi,


Total of 4 numbers --> 4M

Total of 5 numbers --> 5M + 5 x 3 = 5M + 15

So 5th number --> 5M + 15 - 4M = M + 15

M + 15 --> 79
M --> 79 - 15 = 64[/quote]Hi All,

Thanks for your speedy response and wonderful answers