Tutor MathsGuru: Ask me for your burning Maths questions!

[MathIzzzFun]

andante:

gijg:

[quote=\"MathIzzzFun\"]

Hi

Can you explain why they meet at 52km away from city x, should the total distance be 3XY and not 2XY as in ur working. Thank You :salute:

http://i51.tinypic.com/2hezqit.jpg\">

cheers.

Hi,
Am I right to say 2XY is the total distance they travelled after they met at A ? BTW, why is distance travelled by Mr Koh from A to B = 2x64 ??

Thx[/quote]Hi

After they first meet at A, Mr Koh travelled from A-X-B and Mr Tan travelled from A-Y-B, and the total distance travelled ie A-X-B + A-Y-B, is 2XY

It is assumed that both Mr Tan and Mr Koh travelled at constant speed throughout their journeys, Mr Koh travelled 64km in the first part of journey (total distance =XY), and since total distance travelled in the 2nd part of the journey is 2XY, and he would travel 2 x the distance which is 2 x 64km

cheers.

[MathIzzzFun]

rainbow75:

Hi, mathsguru I don't understand why it is 64 *2 -52*2=24 is the answer for the speed question.

Hi

I m not mathsguru...

Mr Koh travelled A-X-B, ie AB + BX + BX = AB+ 2 x 52

since Mr Koh travelled a total of 2 x 64 km from A-X-B,
AB + 2 x 52 = 2 x 64
AB = 2 x 64 - 2 x 52

cheers.

[MathIzzzFun]

Dreamerz:

Thank you Math Guru!

Hi

u r welcome.. btw, I m not mathsguru

cheers.

[MathIzzzFun]

rainbow75:

my kid came back with the working for the first speed question which I have asked earlier , i don't understand can you please explain?

60 mins ----20 km
10 mins ---- 20km÷ 60 = 3 1/3
40 km ÷3 1/3 =12
12× 10 min= 120 min
120min ÷2 =60
60 +20 =80
Can you explain the logic on this working? thank you

Hi

I am not able to extract the train of thought in the provided solution, you may want to check with the teacher. From \"unit of measure\" point of view, the provided solution seemed to be flawed.

60 mins ----20 km
10 mins ---- 20km÷ 6 = 3 1/3 km
40 km ÷3 1/3 km =12
12× 10 min= 120 min
120min ÷2 (** in what unit of measure ??) =60 >> to get km/h, the unit of measure for \"2\" needs to be time^2/km ! eg min.h/km

60 +20 =80

cheers.

[she0407]

Hi, please help to answer the following Qs:


1. Aaron and Devi went shopping with a total of $300 and each bought some items. The amount Aaron spent is three times the amount he has left. The amount Devi spent is twice the amount she has left. Given that the two $90 left, how much did each of them have at first?

2. The number of apples at a store was 80% more than the number of oranges. After 60% of the oranges were sold, there were 42 more apples than oranges. Find the total number of apples and oranges at the store at first.

3. In a school, 60% of the pupils are girls. 10% of the girls and 25% of the boys go to school by car. What percentagee of the pupils go to school by car?

:thankyou:

[MathIzzzFun]

she0407:

Hi, please help to answer the following Qs:


1. Aaron and Devi went shopping with a total of $300 and each bought some items. The amount Aaron spent is three times the amount he has left. The amount Devi spent is twice the amount she has left. Given that the two $90 left, how much did each of them have at first?

:thankyou:

Hi

http://i53.tinypic.com/9icwsn.jpg\">

cheers.

[MathIzzzFun]

she0407:

Hi, please help to answer the following Qs:


1. Aaron and Devi went shopping with a total of $300 and each bought some items. The amount Aaron spent is three times the amount he has left. The amount Devi spent is twice the amount she has left. Given that the two $90 left, how much did each of them have at first?

2. The number of apples at a store was 80% more than the number of oranges. After 60% of the oranges were sold, there were 42 more apples than oranges. Find the total number of apples and oranges at the store at first.

3. In a school, 60% of the pupils are girls. 10% of the girls and 25% of the boys go to school by car. What percentage of the pupils go to school by car?

:thankyou:

Hi

Q2.
Apples : Oranges = 180 : 100 = 9u : 5u

after 60% of oranges sold, oranges left = 40% x 5u = 2u

so 9u - 2u = 7u = 42, 1u = 6

Total number of apples and oranges, at first = 14u = 14 x 6 = 84

Q3.
Girls : Boys = 60u : 40u, total 100u
10% of girls = 10% x 60u = 6u
25% of boys = 25% x 40u = 10u
so, percentage of students who went to school by car
= (10u+6u)/(100u) x 100%
= 16%

cheers.

[wahwah]

Hi MathIzzzFun,


Thanks so much for the explanation. My boy wants to thank you too!

[andante]

MathIzzzFun:

andante:

Hi,
Am I right to say 2XY is the total distance they travelled after they met at A ? BTW, why is distance travelled by Mr Koh from A to B = 2x64 ??

Thx

Hi

After they first meet at A, Mr Koh travelled from A-X-B and Mr Tan travelled from A-Y-B, and the total distance travelled ie A-X-B + A-Y-B, is 2XY

It is assumed that both Mr Tan and Mr Koh travelled at constant speed throughout their journeys, Mr Koh travelled 64km in the first part of journey (total distance =XY), and since total distance travelled in the 2nd part of the journey is 2XY, and he would travel 2 x the distance which is 2 x 64km

cheers.

Sorry to bother again
I don't really understand why 2 x 64 km since Mr Koh travel 64km in the first part ... does it mean XY=64 ??? why ??

Thx

[MathIzzzFun]

andante:

MathIzzzFun:

[quote=\"andante\"]
Hi,
Am I right to say 2XY is the total distance they travelled after they met at A ? BTW, why is distance travelled by Mr Koh from A to B = 2x64 ??

Thx

Hi

After they first meet at A, Mr Koh travelled from A-X-B and Mr Tan travelled from A-Y-B, and the total distance travelled ie A-X-B + A-Y-B, is 2XY

It is assumed that both Mr Tan and Mr Koh travelled at constant speed throughout their journeys, Mr Koh travelled 64km in the first part of journey (total distance =XY), and since total distance travelled in the 2nd part of the journey is 2XY, and he would travel 2 x the distance which is 2 x 64km

cheers.

Sorry to bother again
I don't really understand why 2 x 64 km since Mr Koh travel 64km in the first part ... does it mean XY=64 ??? why ??

Thx[/quote]Hi

eg. if for every 200m, jenny walked 50m, then for every 400m, she would have walked 2 x 50m = 100m since 200m = 2 x 100m; assuming she walked at constant pace.

similarly, for a distance XY, Mr Koh travelled 64km
so for a distance of 2 x XY, he would have travelled 2 x 64 km, for 3 x XY, he would have travelled 3 x 64 km and so forth.

suppose Mr Koh's speed was S1 and Mr Tan's speed was S2, we can divided XY into (S1+S2) parts so that at meeting point A, Mr Koh would have travelled S1 part (=64km) and Mr Tan would have travelled S2 parts.

Now, when the distance is 2 x XY then total number of parts will now be 2 x (S1+S2), and Mr Koh would have travelled 2 x S1 parts = 2 x 64km

cheers.