Tutor MathsGuru: Ask me for your burning Maths questions!

[Millicent]

Dear Mathsguru,


Thanks once again for your great help

[firebird]

Dear Mathsguru and coffeeCat


Good afternoon.

Now I could clearly view mathsguru’s answers.

Many thanks
firebird

[firebird]

Dear Starlight1968sg


Please refer to your request for the following maths.

1) Sophie and Rachel share blue ribbons in the ratio of 5 : 2.
They want to buy some red ribbons so that the total number of ribbons they have will be tripled. In what ratio must they divide the red ribbons so that Rachel will have twice the number of ribbons she has now?

My suggestion:

a) Note, the colour of the ribbon is not an issue for this question.
b) Addition of the ribbons is the real issue here.
c) Let Sophie be S and Rachel be R. Ok so far?
So, S:R = 5:2 Total 7 units (given)
Now S and R want to triple their quantity = 7 x 3 = 21
Therefore, we get S + R = 21
Now R also want to double, but within the quantiy 21.
Therefore R = 2 x 2 = 4
As R is now 4, S = 21- 4 =17

S : R
(Now) 17 : 4
(Originally) 5 : 2 (minus "original" from "now")
-------
12 : 2 (17-5=12 and 4-2=2)
====
To simplyfy further divide 12:2 by 2
We should get 6 : 1

So 6:1 is the ratio of distribution of the addition of ribbons.

2) Faizal has a rod. He needs 6 minutes to saw it into 4 pieces. How many minutes does he need to saw the rod into 28 pieces?

Just take a 10cm string. Imagine it to be a rod. Count and cut 3 times only.
I you will get 4 pieces.

4) There were some horses and people on a farm. There were 62 more legs than heads. There were 26 more heads than tails.

a) How many people were there?
b) How many horses were there?

First of all I assume you know answer to a) which is 26.

Now let total Horses be H, each horse has 4 legs and 1 head
Now let total People be P=26 (answer from a) 26 x 2 = 52 legs and 26 heads

I suggest we Less total heads from total legs as follows:

{52 people legs} + (4 x H)} MINUS {H+ 26 (people head)} = 62 (given)
52 + 4H - H - 26 = 62
3H + 26 = 62
3H = 36
H = 12

I hope the above helps

With best regards
firebird

[/list][/quote]

[P5G]

Pl help.


Paper 1 Q13.
http://www.orlesson.org/orp/09Ma/2009-Math-SA1-MGS.pdf


Worksheet answer is (4) 135 [not likely].


Please advise how to get (3) 125 as Benny's score?


TIA.

[mmmouse]

Anyone knows how to solve this Pr. 3 Maths question?


5 erasers + 3 rulers = S$5.05
3 erasers + 6 rulers = S$3.95
2 erasers + 2 rulers = ???

Thanks!

[CoffeeCat]

mmmouse:

Anyone knows how to solve this Pr. 3 Maths question?


5 erasers + 3 rulers = S$5.05
3 erasers + 6 rulers = S$3.95
2 erasers + 2 rulers = ???

Thanks!

oh wellz its a simultaneous linear equation question.
if 5 erasers + 3 rulers = $5.05
then 10 erasers + 6 rulers = $10.10
and since 3 erasers + 6 rulers = $3.95
then 7 erasers = $6.15
however $6.15 is not divisible by 7 unless there's a mistake somewhere, so its time for another method.

notice that the question is asking for 2 erasers and 2 rulers.
So a quicker method is to combine both information given to derive something like ...

Notice that
5 erasers + 3 rulers = S$5.05 --> (1)
(2 more eraser than rulers)
3 erasers + 6 rulers = S$3.95 --> (2)
(3 less erasers than rulers)

so from (1) we get
15 erasers + 9 rulers = $15.15
(notice 15 is 6 more than 9)
from (2) we get
6 erasers + 12 rulers = $7.90
(notice 6 is 6 less than 12)

(because lcm of 2 and 3 is 6)

so therefore
21 erasers + 21 rulers = $23.05
2 erasers + 2 rulers = ($23.05/21) * 2 = ...

Therefore I have reason to suspect your question is wrong =.=.[/b]

[CoffeeCat]

P5G:

Pl help.


Paper 1 Q13.
http://www.orlesson.org/orp/09Ma/2009-Math-SA1-MGS.pdf


Worksheet answer is (4) 135 [not likely].


Please advise how to get (3) 125 as Benny's score?


TIA.

isn't 125 = 50 + 50 + 25?

[YLH88]

Hi Mathsguru,


Need your help with the below question :

Dan and Mark received some money from their father.
Mark would have $128 more than Dan if Dan gave 2/5 of his share to Mark.
Mark would have $288 more than Dan if Dan gave 2/3 of his share to Mark.
How much money did Dan receive from his father ?

Thank you so much!

[YLH88]

[quote]
YLH88 wrote:
Quote:
Hi YLH88,
While waiting for Mathsguru's model solution, pls see whether mine using ratio is of any use or not?

(a)
D : T
8 : 11
16 : 22

D : T
19 : 19

(16+22)÷2=19

3u=18
u=6
6u=36

At first, Thomas had 36 more game cards than Doran.

(b)
D : T
19:19
38: 38

D : T
3 : 1
57:19

6u=18 [from part (a) ie 6u=36, reduce half of 36 = 18 since 19:19 has been doubled to 38:38 in part (b)]
u=3
19u = 57
Thomas lost 57 more cards to Doran.
Hi Vanilla Cake,

For (a), I got the answer using the model method. For the unit method, why did you change 8:11 to 16:22 ? Why do we multiple by 2 and not 3 or 4 etc ?

For (b), why do you change from 19:19 to 38:38 and 3:1 to 57:19 ?

Thank you!

Hi YLH88,
Sorry for the late reply due to my busy schoolwork.
This is a 4-mark question is from Nanyang 2009 P6 SA1 Paper 2 Q12.

(a) You need to multiply 8:11 by 2 to get 16:22.Add 16+22=38 which is the same as 19+19=38.
(b)19:19 multiply by 2 to get 38:38 so that 38+38=76. And 3:1 multiply by 19 to get 57:19 so that 57+19=76. [/quote]
Hi Vanilla Cake,

Thank you !

[Vanilla Cake]

YLH88:

Hi Vanilla Cake,


Thank you !

Hi YLH88,
You are welcome. My younger sister is also interested to learn the model solution for this problem. While waiting for Mathsguru's model solution, let's use algebra to get the answer.

YLH88:

Dan and Mark received some money from their father.
Mark would have $128 more than Dan if Dan gave 2/5 of his share to Mark.
Mark would have $288 more than Dan if Dan gave 2/3 of his share to Mark.
How much money did Dan receive from his father ?

Case 1
3/5D+128 = M + 2/5D
1/5D+128 = M

Case 2
1/3D+288 = M + 2/3D
288 = M + 1/3D
288-1/3D = M

1/5D+128=288-1/3D
8/15D=160
D = 300

Amount of money that Dan received from his father was $300