**K. 500.** In the ballroom, there are five girls and five boys who would like to waltz. Ann is 160 cm tall, Beth is 165, Carol is 166, Dora is 168 and Emily is 170. Frank is 166 cm tall, Gabe is 168, Hugh is 169, Ian is 172, and Jack is 178. In how many different ways can they form dancing couples if a girl will only dance with a boy if he is taller than herself?

(6 points)

This problem is for grade 9 students only.

**Deadline expired on 11 April 2016.**