Question

1. (number system) the elevation at ground level is 0 feet. an elevator starts 90 feet below ground level. after traveling for 15 seconds, the elevator is 20 feet below ground level. which statement describes the elevator’s rate of change in elevation during this 15 - second interval?

a the elevator traveled upward at a rate of 6 feet per second.
b the elevator traveled upward at a rate of $4\frac{2}{3}$ feet per second.
c the elevator traveled downward at a rate of 6 feet per second.
d the elevator traveled downward at a rate of $4\frac{2}{3}$ feet per second.
\bigcirc a
\bigcirc b
\bigcirc c
\bigcirc d

Explanation:

Step1: Calculate elevation change

Initial elevation: -90 ft; Final elevation: -20 ft. Change = \(-20 - (-90) = 70\) ft (upward).

Step2: Compute rate of change

Rate = \(\frac{\text{Change in elevation}}{\text{Time}} = \frac{70}{15} = 4\frac{2}{3}\) ft/s.

Step3: Determine direction and rate

Elevation increased (upward) at \(4\frac{2}{3}\) ft/s. Matches option B.

Answer:

B. The elevator traveled upward at a rate of \(4\frac{2}{3}\) feet per second.