Question 1106683
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Note that we would be in a much better position to tell you why you are getting the wrong answer if you SHOWED us how you got it....<br>
You want 2 of the 6 she chooses to be blue, which means 4 are red.  There are 7 blue and 6 red remaining.<br>
She is choosing 6 of the remaining 13 fireworks; the number of ways she can do that is "13 choose 6".<br>
You want the probability that of those 6, 2 are blue and 4 are red.  So she needs to choose 2 of the 7 remaining blue fireworks (7 choose 2) and 4 of the remaining 6 red fireworks (6 choose 4).<br>
So the calculation should be straightforward:<br>
{{{(C(7,2)*C(6,4))/C(13,6)}}}<br>
{{{(21*15)/1716 = (7*15)/572 = 105/572}}}