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# Probability watch

1. So I really don't understand this question could someone please explain and show working out answers ect
.

Bill has some counters in a bag
3 of the counters are red
7 of the counters are blue
And the rest of the counters are yellow

Bill takes a counter from the bag

The probability he takes a yellow is 2/7
How many YELLOW counters are in the bag before Bill takes a counter
2. If:

P(yellow) = 2/7
Then, P(Red and Blue) = 5/7

If P(any counter) = no of that counter/total amount of counters

Then:

5/7 = 10/total number of counters
5 x number of counters = 70
Number of counters = 14
14-10=4 yellow counters.

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Updated: June 1, 2016
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