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A jar contains only red, white and blue marbles.It contains twice as many red marbles as white marbles and three times as many white marbles as blue marbles. If a marble is choosen at random, what is the probability that it is not red ?

 

A)\(\frac15\)

B)\(\frac25\)

C)\(\frac35\)

D)\(\frac45\)

 

My answer:

\(\begin{array}{rcll} 2r &=&w \\ 3w\;(or\;6r)&=&b \end{array}\)

 

Alltogether there is 9r marbles the probability of choosing red marble is \(\frac19\)

the probability of not choosing red is \(1-\frac19=\frac89\)

 Mar 31, 2016
 #1
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I figured this way: 6/10 are RED. So, the probability of picking a RED is: 6/10

S0, the probability of NOT picking a RED is: 1 - 6/10=4/10=2/5 or "B"!!!!

 Mar 31, 2016
 #2
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But how did you found that 6/10 are red

Solveit  Mar 31, 2016
 #3
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Use concrete numbers: If there are 100 marbles in the jar, then:

10 are blue

30 are white

60 are red

So, the ratio is 60/100 red marbles or 6/10......etc.

 Mar 31, 2016
 #4
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yes i understood exactly opposite one :/ . Stupid question :)

 

Thank you Guest !

Solveit  Mar 31, 2016

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