Question

A drill can dig through rock at a rate of 2 1/2 inches per hour. How many hours will it take for the drill to reach five feet below the rocky surface, assuming it maintains this rate of digging?

Answer 1

Answer:  24 hours

Step-by-step explanation:

Given : A drill can dig through rock at a rate of $2\dfrac{1}{2}$ inches per hour.

i.e. Speed=  $2\dfrac{1}{2}=\dfrac{5}{2}$ inches per hour.

Formula we use here is : $\text{Time}=\dfrac{\text{Depth}}{\text{Speed}}$

We assume that it maintains this rate of digging.

Since 1 feet = 12 inches

Depth to dig = $5\ \text{feet}=5\times12=60\text{ inches}$

The number of hours it will take  for the drill to reach 5 feet below the rocky surface will be

$\text{Time}=\dfrac{60}{\dfrac{5}{2}}=\dfrac{60\times2}{5}=24$

Hence, it will take 24 hours for the drill to reach five feet below the rocky surface.

Answer 2

5 feet is equal to 60 inches. 60 inches divided by 2.5 inches per hour means it would take 24 hours for the drill to reach five feet (assuming it maintains the same rate of digging)