If we want to have two throws to have the same outcome and the other two being something different, we are essentially looking for three different outcomes in each throw.
We can have three different outcomes in each throw in ^{6}C_{3} ways. We can select the one that is being repeated out of the three outcomes in ^{3}C_{1} ways.
And then, they can be arranged in 4!/2! ways, since there are totally 4 throws out of which 2 are repeated. So, Totally , we can do this in ^{6}C_{3} * ^{3}C_{1} * = * 3 *12 = 20*3*12 = 720 ways.
Correct Answer : 720