Tutor MathsGuru: Ask me for your burning Maths questions!

[Vanilla Cake]

Carrot:

Mr Ho used to travel at a speed of 80km/h from town A to town B. He slowed down his speed to 60km/h and reached town B 1 1/2 hours later than usual. Find the distance between town A and Town B

Constant distance
Ratio of speed
80 : 60
4 : 3

Ratio of time
3 : 4

Difference in time = 1u = 1½ h = 1.5 h

Distance travelled @ 80 km/h -> 3ux80 = 3x1.5x80 = 360 km
or
Distance travelled @ 60 km/h -> 4ux60 = 4x1.5x60 = 360 km

Distance between town A and Town B was 360 km.

OR

Using algebra and let the distance between town A and Town B be D.
Form an equation to solve:

D/80+3/2=D/60
(D+120)/80=D/60
80D = 60D+7200
20D = 7200
D = 360

Distance between town A and Town B was 360 km.

[starlight1968sg]

Hi,

A pet shop owner bought some cans of dog food. He divided the dog food equally among his dogs.
If he bought 7 cans for each dog, he would have bought 4 extra cans.
If he bought 11 cans for each dog, he would need 28 more cans.
(a) How many dogs were there in the pet shop?
(b) How many cans did the owner buy?

I am confused!

Many thanks.

[Brenda10]

starlight1968sg:

Hi,

A pet shop owner bought some cans of dog food. He divided the dog food equally among his dogs.
If he bought 7 cans for each dog, he would have bought 4 extra cans.
If he bought 11 cans for each dog, he would need 28 more cans.
(a) How many dogs were there in the pet shop?
(b) How many cans did the owner buy?

I am confused!

Many thanks.

Hi, the question is familar but can't recall from which paper.

11 - 7 = 4
4 + 28 = 32
32 /4 = 8 (dogs)

8 x 7 + 4 = 60 (cans the owner buy)

Hope the abvoe useful. :lol:

[Yu Xuan]

starlight1968sg:

Hi,

A pet shop owner bought some cans of dog food. He divided the dog food equally among his dogs.
If he bought 7 cans for each dog, he would have bought 4 extra cans.
If he bought 11 cans for each dog, he would need 28 more cans.
(a) How many dogs were there in the pet shop?
(b) How many cans did the owner buy?

I am confused!

Many thanks.

By giving each dog 4 more cans, he use up the extra 4 cans and needed another 28 more.

Hence
28 + 4 = 32
32 / 4 = 8

a) 8 dogs

b) (7 * 8 ) + 4 = 60

[starlight1968sg]

Brenda10:

11 - 7 = 4

4 + 28 = 32
32 /4 = 8 (dogs)

8 x 7 + 4 = 60 (cans the owner buy)

Hope the abvoe useful. :lol:

Why 11 - 7 ?
Then what is \"4 + 28\"?
Can you offer some explanations?
Many thanks.

[Vanilla Cake]

Brenda10:

starlight1968sg:

Hi,

A pet shop owner bought some cans of dog food. He divided the dog food equally among his dogs.
If he bought 7 cans for each dog, he would have bought 4 extra cans.
If he bought 11 cans for each dog, he would need 28 more cans.
(a) How many dogs were there in the pet shop?
(b) How many cans did the owner buy?

I am confused!

Many thanks.

Hi, the question is familar but can't recall from which paper.

11 - 7 = 4
4 + 28 = 32
32 /4 = 8 (dogs)

8 x 7 + 4 = 60 (cans the owner buy)

Hope the abvoe useful. :lol:

Hi Brenda10,
It's from http://www.orlesson.org/orp/09Ma/2009-Math-SA2-ACS.pdf.

Hi starlight1968sg,
To help potential problem solvers in one way or another, pls kindly provide the source of your question and given answer even though the given answer may or may not 100% correct.

Thanks.

[Brenda10]

starlight1968sg:

Brenda10:

11 - 7 = 4

4 + 28 = 32
32 /4 = 8 (dogs)

8 x 7 + 4 = 60 (cans the owner buy)

Hope the abvoe useful. :lol:

Why 11 - 7 ?
Then what is \"4 + 28\"?
Can you offer some explanations?
Many thanks.

Hi, I'm not good in explanation and hopefully you can understand by restate the problem this way:

To give 4 more cans (11 - 7) to reach dog, 32 more cans (4 + 28 ) would be needed

You can refer more this kind of solutions under i-Excel Heuristic and Model Approach - Level 5. I also learn from there and remembered the steps to solve the above question as such. :oops:

[Brenda10]

Vanilla Cake:

Hi Brenda10,

It's from http://www.orlesson.org/orp/09Ma/2009-Math-SA2-ACS.pdf.

Dear Vanilla Cake

Thank you. Now I check and realize we did this quesiton during June holiday that's why I found it familar.

[Carrot]

Yu Xuan:

Carrot:

Hi thank you in advance please help me stuck on this question:


Mr Ho used to travel at a speed of 80km/h from town A to town B. He slowed down his speed to 60km/h and reached town B 1 1/2 hours later than usual. Find the distance between town A and Town B.

:?: :?: :?:
Thanks !

Speed Ratio:
Usual : Slower
80 : 60
4 : 3

Time Ratio
Usual : Slower
3 : 4

4u - 3u = 1 1/2h
1 u = 1 1/2h

1 1/2h * 3 = 4 1/2h
4 1 /2h * 80 = 360km

Is 360km that the answer?[/quote


Thank a lot. I think I understand now.
:boogie:

[corvette]

Dear Gurus,

For the Maha Bodi 2010 Prelim question 18 (the speed question), how is the answer of 40 min derived?

Rosyth 2010 question 16:-
Machine A and B each printed a fixed number of newspapers per hour.
Machine B started printing earlier at a rate of 75 copies per hour. After Machine B had printed for 10 hours, Machine A had printed 340 copies. After Machine B had printed for 16 hours, Machine A had printed 886 copies.
a) How many copies of newspapers did Machine A print per hour?
b) How long would MAchine B hsve worked when both machines have printed a total of 2 750 copies?
Given answer is a) 92 copies per hour
b) 20 hours

Can any help how answer b is derived? Thank you for enlightening me.