Here is a sketch of a Pratt truss, patented in 1844 by two Boston railway engineers, Caleb Pratt and his son Thomas Willis Pratt. Name two triangles from the Pratt truss in the illustration that you would expect to be congruent.

Aclassroom is made up of 11 boys and 14 girls. the teacher has four main classroom responsibilities that she wants to hand out to four different students (one for each of the four students). if the teacher chooses 4 of the students at random, then what is the probability that the four students chosen to complete the responsibilities will be all boys?