1

51. A flight instructor charges $50 per lesson, plus an
additional fee for the use of his plane. The charge for
the use of the plane varies directly with the square root
of the time the plane is used. If a lesson plus 16 minutes of plane usage costs $90, what is the total amount
charged for a lesson having 36 minutes of plane usage?

  • A. $185

  • B. $150

  • C. $135

  • D. $110

  • E. $ 60