Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

livewith_vanilla:

Here is a question I would like some help in.


Source: School paper
Level: P6

A train traveled through a 6500-metre tunnel at an average speed of 25m/s. The whole train took 4 min 30 s to pass through the tunnel completely.
What is the length of the train?

TIA.

Hi livewith_vanilla,

Here's my solution. Hope it helps!


MathsGuru

http://www.postimage.org/image.php?v=gxuHLp0

[livewith_vanilla]

mathsguru:

livewith_vanilla:

Here is a question I would like some help in.


Source: School paper
Level: P6

A train traveled through a 6500-metre tunnel at an average speed of 25m/s. The whole train took 4 min 30 s to pass through the tunnel completely.
What is the length of the train?

TIA.

Hi livewith_vanilla,

Here's my solution. Hope it helps!


MathsGuru

http://www.postimage.org/image.php?v=gxuHLp0

Thanks very much!

Edit: My solution was the same, though I didn't get it. Now i understand.:D

[Almighty]

liketoeat:

Dharma:

[quote=\"liketoeat\"]Hi, please help me solve this question. Thank you.


Candle A and candle B were placed on a table. Candle A was 1.5 cm longer than candle B. Candle A and candle B were lighted at 0630 h and 0800 h respectively. They burnt down to the same length at 1030 h. At 1200 h, candle B was burnt out while A only burnt out at 1230 h. Given that the rate of burning of each candle was constant throughout, find the original length of each candle. (Ans: candle A 13.5 cm; candle B 12 cm)

Time ratio => A : B = 4 : 3
Burning rate ratio => A : B = 3 : 4

Time taken to burn completely
A : 6 hrs (0630hrs to 1230hrs)
B : 4 hrs (0800hrs to 1200hrs)

Length (A ) = 3u x 6 = 18u
Length (B) = 4u x 4 = 16u

18u – 16u = 2u = 1.5cm
Original Length (A) = 18u = 9 x 1.5cm = 13.5cm
Original Length (B) = 16u = 8 x 1.5cm = 12.0cm

Thank you, Dharma.[/quote]Hi Dharma,
Can u pls. explain how u get this step? :?
Time ratio => A : B = 4 : 3

[Maths Monster]

mathsguru:

Dear all...


Just to let you all know tt I'm back... :peekaboo:

:imsorry: My sincere apologies for not being active for the past month. I've taken a 2-week break during the June hols and when I came back, I was busy conducting lessons. :faint:

Finally can catch a breather now since school re-opened! Many thanks to all kind souls who have been helping out here...so many pages to catch up for me!

Hmm...guess I will start solving questions posted from now on instead of trying to catch up with the backlog. Hehe...Hope to seek your understanding!! :please:

Cheers,
MathsGuru

Now that you are back, I will stop posting in your thread. Hope I have help some people here and not be a busy body...anyway, good luck. Cheers, MM

Add - It comes to my notice that when I attached images to some of my previous post, I think some setting are not selected correctly in the \"Add image to post\" option. Hence resulting in unwanted image. I apologize for this. This was never intentional. I have removed all the attachments as best I can. Sorry to all for any inconvenience caused.

[Dharma]

Almighty:

liketoeat:

[quote=\"Dharma\"]
Time ratio => A : B = 4 : 3
Burning rate ratio => A : B = 3 : 4

Time taken to burn completely
A : 6 hrs (0630hrs to 1230hrs)
B : 4 hrs (0800hrs to 1200hrs)

Length (A ) = 3u x 6 = 18u
Length (B) = 4u x 4 = 16u

18u – 16u = 2u = 1.5cm
Original Length (A) = 18u = 9 x 1.5cm = 13.5cm
Original Length (B) = 16u = 8 x 1.5cm = 12.0cm

Thank you, Dharma.

Hi Dharma,
Can u pls. explain how u get this step? :?
Time ratio => A : B = 4 : 3[/quote]Hi Almighty,

At 1030hrs, both candles had the same length.

Candles A takes 2 hrs to burn out ( 1030hrs to 1230hrs ) and candle B takes 1.5 hrs to burn out (1030hrs to 1200hrs).
So, Time ratio => Candle A : Candle B = 2 : 1.5 = 4 : 3

[mathsguru]

Maths Monster:

Now that you are back, I will stop posting in your thread. Hope I have help some people here and not be a busy body...anyway, good luck. Cheers, MM


Add - It comes to my notice that when I attached images to some of my previous post, I think some setting are not selected correctly in the \"Add image to post\" option. Hence resulting in unwanted image. I apologize for this. This was never intentional. I have removed all the attachments as best I can. Sorry to all for any inconvenience caused.

Hey Maths Monster,

Please don't say that! This is not \"my\" thread. It's a learning place for everyone. Your contributions have been priceless (definitely not a busybody!!)! Please do continue to drop by as and when you feel like it and provide your inputs!

As for the attachments, they happen to me and many others too. I'm no IT expert, so my postings are also at the \"mercy\" of the website...haha! I usually choose \"do not resize my image\"...and hopefully it comes out alright.

So, please don't say you're a busybody or that you have caused us any inconvenience...cos u have been nothing but a gem here! Looking forward to seeing you ard here! :please:

Cheers,
MathsGuru

[mathsguru]

Hi all,


Found this candle question quite interesting as it is a typical \"speed\" question in disguise. The key concept here is that the ratio of time taken is the opposite of the ratio of the speeds, provided distances are the same.

This concept is very useful in solving many speed questions, especially when the question does not provide a lot of \"clues\". Therefore, it is a must-know for P6 students!

Here's my solution for your reference!


MathsGuru

http://www.postimage.org/image.php?v=gxxn6ir

[Almighty]

Dharma:

Almighty:

[quote=\"liketoeat\"]

[/quote]
Thankyou very much Dharma and Math Guru.

[Almighty]

Hi All,


The figure below, not drawn to scale, is made up of a circle and 3 identical equilateral triangles. The circle has a radius of 14 cm. Find the perimeter of the shaded parts. Take ^(pie) = 22/7

http://www.postimage.org/image.php?v=Tso6CVr
My Method :
Straight line of a shaded portion is the diameter of that semi circle.
Diameter of the shaded arc = 14cm.So,
Circumference of one shaded semicircle = ( 1/2 ^ D) = 1/2 X 22/7 X14
= 22 cm
22 + 14 = 36 cm (Perimeter of one shaded portion).
So, Total perimeter of the shaded portion = 3 X 36 = 108 Cm

Book method :
Combined all the three arcs together so as to form
curved lenght of shaded parts = curved lenght of semi circle.
Ans: 86cm

MY QUESTION:
Can anyone let me know whats wrong in my method were i assumed each shaded portion as a semicircle with diameter 14cm and not 28 cm.
Hope i am clear !! If not pls let me know. Will TRY to reform the question.

[Almighty]

[quote="mathsguru"][quote="Maths Monster"]Now that you are back, I will stop posting in your thread. Hope I have help some people here and not be a busy body…anyway, good luck. Cheers, MM


NOOOOOO MM .U r such a good tutor. I hv gained a lot thru yr method’s in such a short span. Pls.do support as u were everynow n then. I (WE P6’s) need yr methods.