+0  
 
-1
190
4
avatar

Barry has 4 wooden blocks, 2 are blue, 1 is red and 1 is green. How many ways can he arrange the 4 blocks in a line?

Barrys friend billie is colour blind and cannot distinguish betwwen red and green. How many ways can the blocks be arranged so that billie can see different looks.

 Feb 20, 2020
 #1
avatar+108679 
+1

Barry has 4 wooden blocks, 2 are blue, 1 is red and 1 is green. How many ways can he arrange the 4 blocks in a line?

 

4!/2!=12 ways

 

 

 

Barry's friend Billie is colour blind and cannot distinguish between red and green. How many ways can the blocks be arranged so that Billie can see different looks?

 

4!/2!2! = 6 ways

 Feb 20, 2020
 #2
avatar
+1

How is this worked out? I don't understand what 2!/2! Etc means

 Feb 21, 2020
 #3
avatar+108679 
+1

Fair enough,

I do not know what you know unless you tell me, which you now have. laugh

If you have not studied any probability formally then you will have to just set out all the possibilities in an organized way.

 

Barry has 4 wooden blocks, 2 are blue, 1 is red and 1 is green. How many ways can he arrange the 4 blocks in a line?

BBRG

BBGR

 

GBBR

RBBG

 

RGBB

GRBB

 

BRBG

BGBR

 

BRGB

BGRB

 

RBGB

GBRB

 

THERE IS YOUR 12.

 

Barry's friend Billie is colour blind and cannot distinguish between red and green. How many ways can the blocks be arranged so that Billie can see different looks?

Now copy out those 12 choices.  Bille sees red and green as the same so Chang all the R's and Gs to S (for same)

Now see how many of them are distinguishable. There should be 6.

Melody  Feb 21, 2020
 #4
avatar+108679 
+1

As an aside

6! means 1*2*3*4*5*6

2! means 1*2

 

Is you look on any proper calculator you will find a  ! .  It is called 'factorial'

 Feb 21, 2020

15 Online Users

avatar
avatar