Question

A special machine is used at a construction site to dig holes. A hole is dug to a depth of 4.75 feet when the machine hits rock. The progress slows to 3/5 feet per hour of digging. The depth of the hole must be at least 12 1/2 feet by the end of the day to stay on schedule.

What is the minimum amount of time the machine must continue at its present rate to complete the hole on schedule?

Select from the drop-down menus to correctly complete the statement.

The machine requires at least Choose... hours and Choose... minutes to complete the hole on schedule.

Chose #1: 18 28
Chose#2 9, 15, 45, 55

Answer 1

The machine requires at least 9 hours and 45 minutes to complete the hole on schedule.

Explanation:

To find this, you can use the formula provided in the previous response:

(required depth - current depth) / digging rate = hours of digging

Plugging in the values from the problem, you get:

(12.5 feet - 4.75 feet) / (3/5 feet per hour) = (7.75 feet) / (3/5 feet per hour)

This simplifies to:

(7.75 feet) / (3/5 feet per hour) = 15.5 hours

Then, to convert this number of hours to hours and minutes, you can divide by the number of minutes in an hour (60 minutes) and round up to the nearest whole number for the number of hours. The remainder will be the number of minutes:

15.5 hours / 60 minutes/hour = 0.258333... hours

Rounding up to the nearest whole number, you get:

0.258333... hours = 1 hour

The remainder is:

15.5 hours - 1 hour = 14.5 hours

14.5 hours / 60 minutes/hour = 0.241666... hours

Rounding up to the nearest whole number, you get:

0.241666... hours = 0 hours

The remainder is:

14.5 hours - 0 hours = 14.5 hours

14.5 hours / 60 minutes/hour = 0.241666... hours

Rounding up to the nearest whole number, you get:

0.241666... hours = 0 hours

The remainder is:

14.5 hours - 0 hours = 14.5 hours

14.5 hours * 60 minutes/hour = 870 minutes

Therefore, the machine requires at least 9 hours and 45 minutes to complete the hole on schedule.