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if three straws are chosen at random from a set of 9 straws whose lengths are 1cm, 2cm 3cm, 4cm, 5cm 6cm, 7cm, 8cm, and 9cm find the probability that the three straws will form a triangle. 

Hans007  Feb 11, 2018
 #1
avatar+93658 
+2

if three straws are chosen at random from a set of 9 straws whose lengths are 1cm, 2cm 3cm, 4cm, 5cm 6cm, 7cm, 8cm, and 9cm find the probability that the three straws will form a triangle. 

 

There are 9C3 = 84 ways to chose 3 straws from the 9

They will from a triangle if the sum of the smallest 2 is greater than the length of the longer one.

So just count them. The trick is to dream up a good counting method.

Here is one I dreamed up. I hop I haven't made any silly errors. :)

 

 

So the probability of being able to from a triangle is    33/84

Melody  Feb 11, 2018
 #2
avatar+89953 
+1

I like that "table" trick, Melody.....that makes the counting way easier !!!

 

 

 

cool cool cool

CPhill  Feb 11, 2018
 #3
avatar+93658 
+1

Thanks Chris, it did work rather well - I thought so too   laugh

Melody  Feb 11, 2018

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