A gardener is going to plant 2 red rosebushes and 2 white rosebushes. If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?
~$\frac{1}{12}$~
~$\frac{1}{6}$~
~$\frac{1}{5}$~
~$\frac{1}{3}$~
~$\frac{1}{2}$~
总共是4*3*2*1=24中排列方法
因为4株花都是不一样的, 刚好红花在里面有2中,白花在两端也有2种, (2+2)/24=1/6
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