Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

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.

Radius of the circle = 14cm. So, diameter of circle = 28cm

You had used diameter as 14cm instead of 28cm in your computation of circumference of the semi circle.

[YLH88]

Hi Mathsguru,


Nice to hear from you again Hope you have a good break

[YLH88]

Hi Mathsguru and all,


Need help with the below speed question

A car and a motorcycle set off from Green Town and Pink Town respectively at the same time.
The car, travelling at a constant speed, took 10 hours to reach Pink Town.
The motorcycle, travelling at a constant speed, took 6 hours to reach Green Town.
The vehicles passed by each other when they were 218 3/4 km from Pink Town. Find
a) the distance between the two towns
b) the speed of the car.

Thank you so much!!

[yeodo]

Pls help :


Teck Ming has 30% more stamps than Ravi. Sally has 20% fewer stamps than Ravi. If Teck Ming has 150 stamps than Sally, how many stamps do the three of them have altogether?

[Dharma]

yeodo:

Pls help :


Teck Ming has 30% more stamps than Ravi. Sally has 20% fewer stamps than Ravi. If Teck Ming has 150 stamps than Sally, how many stamps do the three of them have altogether?

Teck Ming : 13u
Ravi : 10u
Sally : 8u

13u - 8u = 5u = 150
1u = 30

No of stamps altogether = 31u = 31 x 30 = 930

[yeodo]

Pls help :


Teck Ming has 30% more stamps than Ravi. Sally has 20% fewer stamps than Ravi. If Teck Ming has 150 stamps than Sally, how many stamps do the three of them have altogether?

[livewith_vanilla]

yeodo:

Pls help :


Teck Ming has 30% more stamps than Ravi. Sally has 20% fewer stamps than Ravi. If Teck Ming has 150 stamps than Sally, how many stamps do the three of them have altogether?

T :R :S
13080
=13 :10 :8

13-8=5
5u->150
1u-> 150/5= 30
31u->30x31=930

Ans: 930 stamps.

Others please confirm with my answer, very unsure if answer is correct,thanks.

[livewith_vanilla]

MOE Hater:

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.

25m/s x 4 min 30 s = 25m/s x 270s = 6750m
6750m - 6500m = 250m

The train is 250m long.

Thanks too MOE Hater!

[mathsguru]

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.

Hi Almighty,

Here's my solution for your reference. The diameter should be 28cm.


MathsGuru

http://www.postimage.org/image.php?v=Pq2vyKJ

[mathsguru]

YLH88:

Hi Mathsguru and all,


Need help with the below speed question

A car and a motorcycle set off from Green Town and Pink Town respectively at the same time.
The car, travelling at a constant speed, took 10 hours to reach Pink Town.
The motorcycle, travelling at a constant speed, took 6 hours to reach Green Town.
The vehicles passed by each other when they were 218 3/4 km from Pink Town. Find
a) the distance between the two towns
b) the speed of the car.

Thank you so much!!

Hi YLH88,

Here's my solution! Funny though...that the car travels so much slower than the motorcycle...

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=Tsp4rcS