<p>The integers 1 through 6 appear on the six faces of a cube, one on each face. If three such cubes are rolled, what is the probability that the sum on the top faces is 17 or 18?
A. 1/108
B. 1/54
C. 1/27
D. 1/18
E. 1/16</p>
<p>I answered A but it is B. Why is that? I am so close to getting 800's on math, but questions like this and "find the number of people who take both X and Y" venn diagram questions screw me up. Help!</p>
<p>It’s either 6, 6, 6 which is 1/6 * 1/6 * 1/6 or 6, 6, 5, the probability is 1/6 *1/6 *1/6 as well. </p>
<p>Also notice that the sequence of the second rolling can be different, you can have 5 in 1st, 2nd or 3rd place. So you should time three for your second rolling</p>
<p>which you got 3 * (1/6)(1/6)(1/6) = 1/72</p>
<p>and the final result will be 1/216+1/72 = 1/54</p>
<p>the possible outcome = 6 * 6 *6 =216
for the sum to be 18 or 17 the numbers must add up in this two ways = 6+6+6 or 6+6+5
u have to notice the sequence of the numbers wht will appear
1 = 6 / 2=6 /3=6
or
2=6 / 1=6/3=6
or
2=6/3=6/1=6
or
3=6/2=6/1=6
so by noticing the sequence u will find that there are only four possibilities that the number will be 17 / 18
4/ 216 = 1 /54 which is b</p>
<p>Thanks! I get it now!</p>