Posted by **Jeffrey** on Sunday, April 24, 2011 at 5:12pm.

In a bag there are 7 red tiles, 3 blue tiles, and 2 purple tiles. How many and what color tiles would you have to add to the bag so that the probability of picking red is 1/3?

- Probability as a Fraction -
**bobpursley**, Sunday, April 24, 2011 at 5:14pm
you want red to be 1/3, you have 7 to choose from, so you want probability to be 7/21. YOu have 12, how many more non red tiles would you add to make 21?

- Probability as a Fraction -
**Damon**, Sunday, April 24, 2011 at 5:17pm
12 in bag now

7/12 are red which is more than 1/3

Say we add x blue tiles

then

7/(12+x) = 1/3

12 + x = 21

x = 9

so add 9 blue tiles for example

check

7 red

12 blue

2 purple

that is 21 total

7/21 = 1/3 check

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