Problem number 21. Three girls and two boys were dancing. They danced in pairs so that each girl danced with each boy for exactly one minute. At any time, there was only one pair on the dance floor. For how many minutes did they dance? A-5, B-6, C-8, D-9, or E-10. The problem asks about the number of minutes that the pairs danced. However, each pair danced for one minute and there was only one pair dancing at a time, so the number of minutes will be the same as the number of pairs. So all we need to find is the number of pairs that were made by these three girls and two boys. There were three girls and two boys. The pairs were made from each girl dancing with each boy. So the first girl danced with two boys, so she danced with each one of them. So there were two pairs that included the first girl. The second girl also danced with each of the two boys, so there were two pairs that included the second girl. And the third girl danced with each of the two boys, so there were two pairs that included the third girl. Two plus two plus two is six, so there were six pairs. And we already figured out that six pairs would dance for six minutes total, so the answer is B, six.

dance pairs

girls and boys

total dance time

pair formation

six minutes