Question

Denise and Donna want to exchange secrets from across a crowded whispering gallery. Recall that a whispering gallery is a room which, in cross section, is half of an ellipse. If the room is 30 feet high at the center and 90 feet wide at the floor, how far from the outer wall should each of them stand so that they will be positioned at the foci of the ellipse? Fill in the blank: Denise and Donna should each stand _____ ft from the outer wall so that they will be positioned at the foci of the ellipse. Round your answer to the nearest whole ft (no decimal places).

Answer 1

Answer:

34 feet

Step-by-step explanation:

From the question, we are told that:

If the room is 30 feet high at the center and 90 feet wide at the floor,

Entire width of the room = 90 feet = 2a

a = 90/2 = 45

Height of the room = b = 30 feet

Foci (c)² = a² - b²

c = √a² - b²

c = √45² - 30²

c = √1125

c = 33.541019662 feet

Approximately to the nearest whole number = 34 feet

Denise and Donna should each stand 34 ft from the outer wall so that they will be positioned at the foci of the ellipse