lara is setting up a convention room. she is expecting 240 attendees and can comfortably fit chairs in rows of 16. how many rows does she need to set up?

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?