Question 1102796
1-3-3-1: 0 heads (1), 1 head (3) 2 heads (3), 3 heads (1).  At least 2 heads is 4/8 or 1/2.
HHH
HHT
HTH
HTT
THH
THT
TTH
TTT
HTH has a probability of 1/8
At least two heads is  1/2
At most 2 heads is 7/8.
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1==2==4==8==16==32
The median is the middle of 6, which has no defined middle term. Therefore, it is the average of the terms on either side of the middle, which are 4 and 8.  Their average is 6.  The mean is the sum divided by 6, or 10.5.  This is higher, because the distribution has two numbers (16 and 32) significantly larger than the others.
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25 marbles altogether
2 yellow is 4/25*4/25=16/625 or 0.0256
at least one red marble is 7/25*18/25+18/25*7/25+7/25*7/25, which is probability of both being red.
that is (126+126+49)/625=301/625.