Amultiple-choice test contains 10 questions. there are four possible answers for each question. (a) in how many ways can a student answer the questions on the test if the student answer every question? (b) in how many ways can a student answer the questions on the test if the student can leave answers blank?

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?