Tutor MathsGuru: Ask me for your burning Maths questions!

[MathIzzzFun]

wahwah:

Hi MathIzzzFun,

Thanks for the solution. But can you explain the model for Q2, my boy can't understand it though he has been looking at it since Saturday.

Hi

I have added two more arrows in the model

http://i52.tinypic.com/21cuk8z.jpg\">

The blue arrow shows how the average marks increase when a new score (100) which is higher than the original average is added, and the red one shows how the average marks decrease after a new score which is lower than the original average mark is added.

When a new score of 100 is added, the overall average is 90. So the difference of (100-90) is divided among existing students to bring up the average.

Similarly, when a new score of 60 is added and the overall average becomes 85, in this case, the \"added\" marks of (85-60) for the new student is being contributed equally from the existing students.

Another way is look at is : imagine the original average mark as water level in a container, and adding a new \"tube\" with a higher water level so that the final water level in both the container and the tube reaches the same new level.

cheers.

[aiong]

Good morning, need help on the following math question, thank you


David has 4 times as many stickers as Ali. If David has 2160 more stickers than Ali.
How many stickers does they have altogether?

[sanie]

Can help with this qn. thanks


The ratio of $1 notes to $5 notes in Henry’s wallet is 2:3. If Henry exchanges 24 pieces for $5 notes for some $1 notes, he will have 12 times as many $1 notes as $5 notes. What is the total value of $1 notes and $5 notes in Henry’s wallet?

[wahwah]

Hi MathIzzzFun,

Thanks so much for the explanation. My boy understands now.

[amirtha]

Dear Maths Guru


Could you pls help to solve the below P6 question.


http://i56.tinypic.com/33m0nm1.jpg\">


thks

[MathIzzzFun]

wahwah:

Hi MathIzzzFun,

Thanks so much for the explanation. My boy understands now.

hi wahwah,

you are welcome :lol:

cheers.

[PiggyLalala]

Sun_2010:

amirtha:

Dear Maths Guru


Could you pls help to solve the below P6 question.


http://i56.tinypic.com/33m0nm1.jpg\">


thks

The solution is a bit tedious to explain in detail. Hope this is clear.

1.Area of triangle ACD = = 1/2 Area of square ABCD
= Area of triangle AFE + Area of quadrilateral EFCD
2. Area of triangle AFE + Area of triangle BFC= 1/2 Area of square ABCD

From 1 and 2 ,
Area of quadrilateral EFCD = Area of triangle BFC

Area of triangle BFC +Area of quadrilateral EFCD
= Area of quadrilateral EBCD
= Area of square ABCD - Area of triangle ABE
= 12x12 - 6x12/2 = 108

Area of quadrilateral EFCD =108/2 = 54

Note: Point 2 is true for any point in a square

Area of quadrilateral EFCD = 108/2

Thank you for the solution. However, i do not quite understand this step.
Area of triangle AFE + Area of triangle BFC= 1/2 Area of square ABCD :?

[Brenda10]

amirtha:

Dear Maths Guru


Could you pls help to solve the below P6 question.


http://i56.tinypic.com/33m0nm1.jpg\">


thks

Hi, extracted answer from dd working:


4 x 4 = 16
16 /2 = 8
1/2 x 2 x 4 = 4
8 + 4 = 12
1/2 x 12 x 12 = 72
72 -12 = 60

Answer: 60cm2

[Chan09]

Need some help:

Mary spent $85 on food and $45 on transport. After that she spent 2/7 of the remaining money on 4 books. As for the rest of the money, she gave 2/5 of it to her sister and had $75 left.
A) how much did each book cost?
B) how much money did she have at first?
Thank you
I tried the branch method but did not get the correct answer.

[Brenda10]

Chan09:

Need some help:

Mary spent $85 on food and $45 on transport. After that she spent 2/7 of the remaining money on 4 books. As for the rest of the money, she gave 2/5 of it to her sister and had $75 left.
A) how much did each book cost?
B) how much money did she have at first?
Thank you
I tried the branch method but did not get the correct answer.

Hi Chan09,

We would like to ask you is the answer for (a) $12.50 and (b) $305 ?