A cylindrical thermos has a radius of 4 in. and is 5 in. high. It holds 40 fl oz. To the nearest ounce, how many ounces will a similar thermos with a radius of 3 in. hold?

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?