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Primary 5
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Number and Algebra
Got the answers on the right side. But using the lengthy method. Anyone has a shorter solution. Please help though it is not a model question thanks
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13
Rye Tan
There is.... but i need time to think of how to explain it
6 years ago
Rye Tan
Number of ways = 6-C-3
= 6! / ( 3! x 3! )
= 20
6 years ago
Rye Tan
I would try using the "box method"....
as you can see, there are 3 slots available for 6 players. For "player 1" slot, all 6 kids can be chosen. So we will have 6 possible cases for "player 1" slot.
For "player 2" slot, we only have 5 kids to choose from, as the sixth child has been chosen to be player 1.
For the "player 3" slot, there are only 4 kids left to choose from.
Hence, the number of ways to choose 3 kids out of 6 kids, WITH A SPECIFIC ORDER, is given by
6 x 5 x 4 = 120.
6 years ago
Shirley Wee
Hi, thank you for taking the time to explain. Sorry for being thickheaded but I understood until the 6 x 5 x 4 step. May I ask why is it multiplied? I get that you divide by 6 to get the answer.
6 years ago
Rye Tan
Because there are 5 possible ways to select player 2 for each of the 6 possible ways to select player 1.
ie
you have 6 ways to select player 1.
no matter whom is selected as player 1, there will be 5 choices for you to choose player 2, FOR EACH OF THE 6 DIFFERENT WAYS YOU SELECT PLAYER 1.
6 years ago
Shirley Wee
I see, I see. Thank you Rye for clearing this up. 👍
6 years ago
Rye Tan
Using the branching method....
6 years ago
Rye Tan
Each red rectangle shows 1 possible way of choosing the player 1. Since there are 6 kids, There are 6 rectangles. ( 1 kid ---> 1 possibility)
Next, each of the possible way of choosing player 1 will lead to 5 possible choices to choose player 2, (denoted by 5 C.)
Hence, total number of ways to choose 2 kids from 6 kids, IN AN ORDERED MANNER. is 6 x 5 = 30
6 years ago
Shirley Wee
Thanks will try to figure out
6 years ago
Rye Tan
However, in the case of the question, the order of the 3 players DO NOT MATTER.
As you can see below, for any 3 players "denoted by different coloured cubes", there are 6 ways to arrange them.
In this question, these 6 methods to group 3 players are all considered as 1 way of grouping.
So,
Number of ways of grouping = 120 / 6
= 20
6 years ago
Shirley Wee
Oh okay I think I get it now. Thank you very much for your time and help and visual explanation!
6 years ago
Megan Wong
Hi Shirley, is this P6 work?
6 years ago
Shirley Wee
No its P5 work, so tough
6 years ago
Shirley Wee
Hi, thank you for taking the time to explain. Sorry for being thickheaded but I understood until the 6 x 5 x 4 step. May I ask why is it multiplied? I get that you divide by 6 to get the answer.
6 years ago
Rye Tan
Because there are 5 possible ways to select player 2 for each of the 6 possible ways to select player 1.
ie
you have 6 ways to select player 1.
no matter whom is selected as player 1, there will be 5 choices for you to choose player 2, FOR EACH OF THE 6 DIFFERENT WAYS YOU SELECT PLAYER 1.
6 years ago
Shirley Wee
Oh okay I think I get it now. Thank you very much for your time and help and visual explanation!
6 years ago
Shirley Wee
I see, I see. Thank you Rye for clearing this up. 👍
6 years ago
Rye Tan
Using the branching method....
6 years ago
Rye Tan
Each red rectangle shows 1 possible way of choosing the player 1. Since there are 6 kids, There are 6 rectangles. ( 1 kid ---> 1 possibility)
Next, each of the possible way of choosing player 1 will lead to 5 possible choices to choose player 2, (denoted by 5 C.)
Hence, total number of ways to choose 2 kids from 6 kids, IN AN ORDERED MANNER. is 6 x 5 = 30
6 years ago
Stella Lee
Asked 9 years ago
SG
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Primary 5
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Geometry
P5 qn, pls help on qn (b), TIA
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3
Shaoyang Brandon
Hi, Stella. The key to this question is to use the property that the 3 angles of a triangle add up to 180 degrees.
See image for further details. :)
6 years ago
Stella Lee
TYSM!! :)
6 years ago
Stella Lee
6 years ago
Adrian Ng
Asked 9 years ago
SG
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Primary 4
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Number and Algebra
Making it visual...
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1
Feiny Chen
My little girl can understand. Thank you very much
6 years ago
Stella Lee
Asked 9 years ago
SG
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Primary 5
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Number and Algebra
P5 an, pls help, TIA
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3
Mayuree Thongpan
6 years ago
Mayuree Thongpan
6 years ago
Stella Lee
Thks
6 years ago
Feiny Chen
Asked 9 years ago
SG
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Primary 4
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Number and Algebra